Re the overheating message when using a PocketWizard Flex TT5 - I saw that last night (though it seems to be fine this morning) - and I put it down to confusing communications on the hotshoe; incompatibilities between Canon protocols and Fuji ones.
That may or may not have been the issue, but I did work around it:
http://statusq.org/archives/2016/03/20/7463/
and this system seems to work nicely for me.
Quentin