A few months ago I replaced the worn out bottom bracket on one of my old bikes hat has Nuovo Record crankset.
I installed a new Phil Wood 115mm ISO BB and was able to align the chainline perfectly with the adjustable cups.

Last week I started having trouble shifting (friction shifter 12-speed) and noticed my chainline had moved 4mm to the RH side.

I remember measuring the BB before installing it and noticed the spindle was symmetrical, but now when I measured I see that it is no longer symmetrical, one side sticks out 23mm and the other is 32mm.

How could the spindle have moved to the RH side all by itself?