Minecraft 1.14.4, tested on the most recent 0.2 build

issues:
placing a mechanical piston down or placing a pulley without any attached blocks and making them extend down will break any block below them. this includes unmovable blocks like obsidian and bedrock.

plain mechanical pistons will stick to blocks even though they are not sticky

sometimes while extending mechanical pistons or retracting them or changing directions the piston head will either visually disappear or fly away

rotational bearings, if attached to/ next to an immovable block in its range, will be unable to be moved.

Most of these should be taken care of by now.
The moving contraption system is known to not being feature-complete and an unstable mess. We have the known issues internally and would love to hear of bugs we missed once an alpha build of 0.2 is released.