Various Verrou-inspired fixes

While rebasing and re-testing !490 (merged), I noticed that I had a whole bunch of new Verrou failures. As usual, some were false positives and others hinted at a genuine issue or smell in the code.

Every failure that fundamentally came from a bad float comparison threshold was directly fixed in !490 (merged). This MR is meant to collect the other fixes that I carried out along the way, which do not really belong to !490 (merged).