Do you know, that… ?

Assemblies have moving and fixed parts.

The latter type may result from activating the Fixed option (f) or from the definition of such bonds, which definitively determine the position in the assembly by receiving appropriate degrees of freedom.

View, how you can find non-moving parts regardless of level, what they are on (may be in subassemblies).

on the Review select Assembly visualization. Insert a new column and select Fully fitted.

Entries will appear in this column Yes or No, of course yes means full match. The problem is solved:)