While I can't address your specific issue, I can tell you that in my own personal experience VIMs work less well the more nesting they contain. If you have any VIMs inside of your VIM, see if you can reduce the nesting.
If there's a VIM in a VIM, consider right-clicking the inner VIM and choosing the "Replace with SubVI contents" option. This gives you the same code with the drawback that you don't get any updates to the inner VIM if it has code that might get updated separately, but many nested VIMs are in my experience the "Assert" VIMs or other very simple ones that shouldn't matter if they get disconnected from the source VIM permanently (things like "Stall data flow", for instance).
Also, weirdly enough it seems that sometimes a "Mass compile" or other recompile won't fix a broken VIM, or VI containing a VIM, but deleting the wires leading to the VIM and reconnecting them does. I suspect doing so forces it to re-run the type propagation code again from the beginning, which sometimes it seems doesn't work like it should if the wire passing through it gets an updated type (via type definition update or class private data update).
