I tried manually scrubbing my iMangler of all IDM plugins and recreating my RBS collection, reinstalling etc. No dice.
It is 2.7.1 with the latest 3.6 IR plugins.
On the working tree I have the same versions (or at least I thought I did) which shows for the dozen or so IDM plugins, except the base IDM plugin which still shows 3.5. But all of the ones being presented are the 3.6 plugins not the 3.5 so I'm just super confused now.
This is the TID I used to scrub:
plus some common sense for the new version names.