My Kossel Mini printer was working well. Recently I made some changes including replacing the nozzle and throat, adding a silicone heater cover. Now it has the problem of first layer adhesion.
The perimeter sticks well but the infill line swells upward in the middle, while start and end has no problem.
In my experience the adhesion problem only occurs at corner but never in the middle. So I don't know what configuration needs to be changed to fix it.
Delta calibration has been done before the print. PVP glue was used on the bed.