Hi Alexandre,
Since I currently have my head wrapped around the d3d message tests I'd like to give your fvwm2 test failures another try. Can you send me the test failures you currently see?
Here I see one failure mostly reliably (~90% of all runs) with fvwm2 in focus follows mouse mode. I think the particular test is not too important, so we can disable it, but I'd like to verify first that it is the same issue you have.
Cheers, Stefan