in my kit, the front panel PCB was not parallel with the front panel:
inserting a 1mm or 2mm thick washer between the rotary encoder and the front panel fixes this:
C13
on the PSU board.
drill a hole in the chassis below the board's screw hole and use a self-tapping screw to secure the PSU:
this diagram from Banggood shows how to wire the handle. be sure to solder in the vibration switch the correct way:
it's easier to solder the handle cable to the surface pads on the handle PCB:
it looks like loading a tip into the handle causes the PCB to bend quite a bit. the handle may be the first part that breaks: