The problem is every file I have.
Plain Autocad through Design Suite
Yes 3D and Yes quite a few Xrefs....file size varies but it is slow for all.
An other idea : did you try to remove all possible Scale Annotations ?
( in ALL yours DWGs : the Main DWG and ALL XREFs )
Please Remove ALL possible Scales ... and resave the DWG ...
Normal Value is 2 (two) for layoutregenctl ...
It consumes a liitle bit more memory, but the switching is faster (No Regen)