This is often called mosaic and modularity, which means poor consistency.

The reason is:

The plug-in is too tight for the wave soldering fixture to correct.

If the wave soldering fixture is not good, the lamp will come out crooked.

The lamp holder does not match the lamp type, and the package size of each LED lamp is different, even if the gap is 0. 1mm, the impact is great. Every brand of LED can't be universal, so we need to make a new fixture.

Plastic surgery. Plastic surgery is an immature process, and it is best to go. Inconsistent plastic strength, tool tolerance and other factors.

The bottom case is assembled, the PCB is not fully in place, and the lamp is floating high.