I think you need to revise all your blocks, for example I noticed that in one of the blocks inside your drawing; FM - F1AS9N-1A12-10S, there are another blocks which seems lined up, but if I zoom deep enough to the object corners in this block (I explore this block in Block Editor), I can see this:

the objects doesn't lined up correctly.

So it is possible that when you use END object snap you accrue wrong endpoint inside your blocks - this gives an error in aligning blocks.

Maxim