Items Flopping through and open-ended shroud (or: how did I even do that in the first place?!)

[Jestersage]

So I am updating my Apollo-Saturn V clone, and after create a subassembly of the new MEM, I removed the MEM from the "Ananas YiX Munar + Fogin SiCC" and drop in the new MEM.

Problem is that while the old stack doesn't flop around, the new stack does (specifically, the CSM flop around the top shroud that function as LM-adapter). As far as I recall, I did not change any auto struct settings for those unrelated to the MEM. I also ensure the top port and the terrier (the top and bottom attackment nodes of MEM) are autostrut to heavy,

Would someone please give me pointer as to why the CSM seems to flop through the top shroud?

EDIT: Okay, guess it's MEM itself -- something that cause it flopping around, but it was fine before I put the BG robotics for the rover deployment....
EDIT2: yes, temporary stop gap solution is to use interstag node for the shrouds and put a TS-decoupler. However, in the earlier version I can do it without such contraption.

Edited June 2, 2019 by Jestersage