Assembly wants to update current parts; refuses to update old parts.

[i-make-robots]

I've been building a stewart platform.  I made subassemblies for

- a motor on it's mount,

- a forearm (rod + ends),

- a pair of arms assembled with their motors (mirrored motor), and finally

- the top plate

- a master assembly of all components (used a rotation pattern to copy the sub assembly).

Ground appears to be ignored at random.  Sometimes I pull the top plate (blue) and the grounded motors go flying away. 

I also get strange update warnings.  in the attached image I'm being told that the forearms are not up to date, tho they are.  Yesterday the app insisted that one of the two motors in the pair of arms assembly was out of date, and clicking update did nothing.

Today I'm getting: "This design contains Removed components which did not update. To complete the update, roll the history marker to before the earliest Remove feature and click the Get All Latest button. 2 Components are still out of date. Please run the Get All Latest command again."  I haven't removed anything!  There's no remove feature on the timeline.  Rolling back to every point on the timeline and trying again makes no difference.

I'm not mad, I'm exhausted.  Please tell me what I'm doing wrong.

Also here it is animated, one of the times it behaved: https://www.instagram.com/p/BR1p9Msgd5P/

[i-make-robots]

And here's what happens when I drag it in a "bad" way.  I have joint limits so I shouldn't be able to drag it to an unsolvable position.

When this happens undo will not restore the parts to their proper positions.  I have to rebuild the assembly from sub-assemblies and recreate the joints.

That's what's exhausting.