Place a Mechanical Bearing facing either left or right in a structure. Then turn that structure into a Minecart Contraption. After assembly, the bearing immediately rotates what's in front of it on the y-axis despite its orientation on the x or z axis, and without any movement from the minecart. Below are screenshots of this occurrence:

#1
First, the structure as it is intended to be.

#2
Then, when redstone power is applied and the contraption is assembled, the arms with drills turn to face forwards:

#3
Lastly, when unpowered, the structure remains turned in this unexpected way:

I assume this is not intended behaviour of Mechanical Bearings in a Minecart Contraption.

EDIT:
I should note that changing the properties of contraption actors via the Cart Assembler does not affect this behaviour.
Furthermore, repeated assembling and disassembling of the contraption repeats the effect, rotating what is in front of the Mechanical bearing repeatedly.

This is patch f 1.20.1:

Can confirm this for versions down to 0.3.2f and also on 1.19.2/1.18.2 in 0.5.1b.

Another issue that can be seen in screenshot 2 (recreated here for clarity) is that stabilized contraptions appear to be 2 pixels too low

Let me know if I should make a separate issue for this

Another issue that can be seen in screenshot 2 (recreated here for clarity) is that stabilized contraptions appear to be 2 pixels too low

Let me know if I should make a separate issue for this

a separate issue would be nice yeah