PSU is only feeding 12 V into RAMPS, but (if I remember correctly) RAMPS is using Arduino's onboard regulator for converting 12 V to 5 V. That regulator can not provide much power.
If you connect some significant load to any 5 V pin (like servo, LCD backlight, or BLTouch), the regulator will be overloaded and its output voltage will drop (too low or unstable ...
You could download the firmware version directly from the vendor and choose the one that is supposed to be on the board when it was shipped to you.
Put the bin file on the SD card from your laptop/computer and reinsert the SD card in the printer and start the printer.
The problem turned out to be mechanical. The arm that I mounted the camera on had developed a crack where it connects to the build platform. I used some superglue to repair the crack and the camera shaking went away.
The lesson here is to check EVERYTHING mechanical before trying to blame shaking on the firmware.
Instead of changing firmware or changing the wiring, I flipped the motor direction. See the first photo below. Motor shaft was on the right side, now, the motor shaft is on left side, so the the bed moves backwards. I moved the Y endstop to back and now it prints fine.
only the problem is
if I press -Y -- bed moves backward (towards the Y ...
For most Cartesian printers, the homing position is at the front-left corner of the build plate. End-stop switches can be at either end of each axis (and even both), but the firmware must be configured accordingly.
A common arrangement is to have end-stop switches at X-min, Y-min and Z-min positions. You will see this on pretty much all budget printers, but ...