i have made a create cart tank for fun, and the tank includes a turret built on a mechanical bearing.
when formed, the entire cart becomes an entity, as you would expect. (image shown, turret blocks not being picked up by WAILA = turret is currently an entity)

however upon being picked up the turret does not come with the contraption (see the cart contraption in my inventory and the turret which is now solid blocks is not with the contraption)

this makes me sad as i wanted to develop my tank in a safe location then transport it via inventory to the desired location, however it seems i will need to make a whole new turret each time

idea: you could set the turret to solid blocks before putting it on the cart

they are, when the create cart is formed they become an entity, but before that they are solid blocks

getting the same bug here on above and beyond version 1.1 modpack
basically the problem is
It seems like any sub-structure that is anchored by a mechanical bearing cannot be stored/formed into a minecart contraption

so for example, if we have something as simple as this
https://cdn.discordapp.com/attachments/689866656914210897/909194751121711145/unknown.png

nothing that is connected after the mechanical bearing will be formed as part of the minecart contraption

or a more complicated one where there are two nested gantry systems and a final mechanical bearing sub structure
before assembling:
https://cdn.discordapp.com/attachments/689866656914210897/909195367101374474/unknown.png

after assembling:
https://cdn.discordapp.com/attachments/689866656914210897/909195560924373042/unknown.png

as you can see the linear chassis is detached after being assembled as a minecart contraption.

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

this is not stale, please do not delete it

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

not stale, still no official comment

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

not stale, please fix

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

not stale

oh gosh

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

no