Why is some part of the print not aligned?

Question

I'm using a Prusa Slicer with a FlyingBear Ghost 4 and got a wrong printing alignments on the Y axis only on a part of the printing object. What may cause this?

Here are the printed model pictures showing the problem:

Here are the settings:

# generated by PrusaSlicer 2.1.0+win64 on 2019-09-29 at 11:37:50 UTC
avoid_crossing_perimeters = 0
bed_custom_model = 
bed_custom_texture = 
bed_shape = 0x0,255x0,255x210,0x210
bed_temperature = 60
before_layer_gcode = 
between_objects_gcode = 
bottom_fill_pattern = rectilinear
bottom_solid_layers = 7
bridge_acceleration = 0
bridge_angle = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 0
clip_multipart_objects = 0
colorprint_heights = 
complete_objects = 0
cooling = 1
cooling_tube_length = 5
cooling_tube_retraction = 91.5
default_acceleration = 0
default_filament_profile = ""
default_print_profile = 
deretract_speed = 0
disable_fan_first_layers = 3
dont_support_bridges = 1
duplicate_distance = 6
elefant_foot_compensation = 0
end_filament_gcode = "; Filament-specific end gcode \n;END gcode for filament\n"
end_gcode = M104 S0 ; turn off temperature\nG28 X0 Y0 ; home X and Y axis\nM84     ; disable motors\n
ensure_vertical_shell_thickness = 0
external_perimeter_extrusion_width = 0.45
external_perimeter_speed = 50%
external_perimeters_first = 0
extra_loading_move = -2
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extruder_colour = ""
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = 1
extrusion_width = 0.45
fan_always_on = 0
fan_below_layer_time = 60
filament_colour = #FFFFFF
filament_cooling_final_speed = 3.4
filament_cooling_initial_speed = 2.2
filament_cooling_moves = 4
filament_cost = 30
filament_density = 1.25
filament_deretract_speed = nil
filament_diameter = 1.75
filament_load_time = 0
filament_loading_speed = 28
filament_loading_speed_start = 3
filament_max_volumetric_speed = 0
filament_minimal_purge_on_wipe_tower = 15
filament_notes = ""
filament_ramming_parameters = "120 100 6.6 6.8 7.2 7.6 7.9 8.2 8.7 9.4 9.9 10.0| 0.05 6.6 0.45 6.8 0.95 7.8 1.45 8.3 1.95 9.7 2.45 10 2.95 7.6 3.45 7.6 3.95 7.6 4.45 7.6 4.95 7.6"
filament_retract_before_travel = nil
filament_retract_before_wipe = nil
filament_retract_layer_change = nil
filament_retract_length = nil
filament_retract_lift = nil
filament_retract_lift_above = nil
filament_retract_lift_below = nil
filament_retract_restart_extra = nil
filament_retract_speed = nil
filament_settings_id = "FlyingBear Ghost 4"
filament_soluble = 0
filament_toolchange_delay = 0
filament_type = PLA
filament_unload_time = 0
filament_unloading_speed = 90
filament_unloading_speed_start = 100
filament_wipe = nil
fill_angle = 45
fill_density = 20%
fill_pattern = stars
first_layer_acceleration = 0
first_layer_bed_temperature = 60
first_layer_extrusion_width = 0.42
first_layer_height = 0.2
first_layer_speed = 30
first_layer_temperature = 210
gap_fill_speed = 20
gcode_comments = 0
gcode_flavor = marlin
gcode_label_objects = 0
high_current_on_filament_swap = 0
host_type = octoprint
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0.45
infill_first = 0
infill_only_where_needed = 0
infill_overlap = 25%
infill_speed = 80
interface_shells = 0
layer_gcode = 
layer_height = 0.1
machine_max_acceleration_e = 10000,5000
machine_max_acceleration_extruding = 1500,1250
machine_max_acceleration_retracting = 1500,1250
machine_max_acceleration_x = 9000,1000
machine_max_acceleration_y = 9000,1000
machine_max_acceleration_z = 500,200
machine_max_feedrate_e = 120,120
machine_max_feedrate_x = 500,200
machine_max_feedrate_y = 500,200
machine_max_feedrate_z = 12,12
machine_max_jerk_e = 2.5,2.5
machine_max_jerk_x = 10,10
machine_max_jerk_y = 10,10
machine_max_jerk_z = 0.2,0.4
machine_min_extruding_rate = 0,0
machine_min_travel_rate = 0,0
max_fan_speed = 100
max_layer_height = 0
max_print_height = 200
max_print_speed = 80
max_volumetric_speed = 0
min_fan_speed = 35
min_layer_height = 0.07
min_print_speed = 10
min_skirt_length = 0
notes = 
nozzle_diameter = 0.4
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 1
parking_pos_retraction = 92
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0.45
perimeter_speed = 60
perimeters = 4
post_process = 
print_host = 
print_settings_id = FlyingBear Ghost 4
printer_model = 
printer_notes = 
printer_settings_id = FlyingBear Ghost 4
printer_technology = FFF
printer_variant = 
printer_vendor = 
printhost_apikey = 
printhost_cafile = 
raft_layers = 0
remaining_times = 0
resolution = 0
retract_before_travel = 2
retract_before_wipe = 0%
retract_layer_change = 0
retract_length = 2
retract_length_toolchange = 10
retract_lift = 0
retract_lift_above = 0
retract_lift_below = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
seam_position = aligned
serial_port = 
serial_speed = 250000
silent_mode = 1
single_extruder_multi_material = 0
single_extruder_multi_material_priming = 1
skirt_distance = 6
skirt_height = 1
skirts = 1
slice_closing_radius = 0.049
slowdown_below_layer_time = 5
small_perimeter_speed = 15
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0.45
solid_infill_speed = 20
spiral_vase = 0
standby_temperature_delta = -5
start_filament_gcode = "; Filament gcode\n"
start_gcode = G28 ; home all axes\nG1 Z5 F5000 ; lift nozzle\n
support_material = 1
support_material_angle = 0
support_material_auto = 1
support_material_buildplate_only = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0.35
support_material_interface_contact_loops = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = rectilinear
support_material_spacing = 2.5
support_material_speed = 60
support_material_synchronize_layers = 0
support_material_threshold = 0
support_material_with_sheath = 1
support_material_xy_spacing = 50%
temperature = 210
thin_walls = 1
threads = 4
toolchange_gcode = 
top_fill_pattern = rectilinear
top_infill_extrusion_width = 0.4
top_solid_infill_speed = 15
top_solid_layers = 9
travel_speed = 150
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
variable_layer_height = 1
wipe = 0
wipe_into_infill = 0
wipe_into_objects = 0
wipe_tower = 0
wipe_tower_bridging = 10
wipe_tower_rotation_angle = 0
wipe_tower_width = 60
wipe_tower_x = 180
wipe_tower_y = 140
wiping_volumes_extruders = 70,70
wiping_volumes_matrix = 0
xy_size_compensation = 0
z_offset = 0

Answer 1

This looks like your problems are lack of retraction and having the slicer's "overhangs" setting enabled.

Retraction is absolutely essential when your print has layers with multiple disconnected components, and even when it doesn't, it's usually important. Without retraction, material will continue to flow out of the nozzle after extrusion is supposed to have stopped, producing oozing/stringing and subsequent underextrustion (due to the material already having been lost elsewhere).

The "overhangs" setting is actively harmful unless your printer firmware has "linear advance" feature and you have calibrated it properly. Otherwise, when reaching part of the perimeter that's an overhang, the print head motion will slow down (I think PrusaSlicer does 10-20 mm/s for overhangs), but extrusion will continue at the full previous rate until pressure in the nozzle subsides. This is what's causing all the ugly sagging loops around the tail. Disable this misfeature so that print speed remains constant between overhang and non-overhang parts of the perimeters.