Hi William,
We made a very minor Qt update for Gaffer 1.5 - upgrading from Qt 5.15.12 to Qt 5.15.14. It seems unlikely to be the cause of the problem, but anything is possible of course.
Is the PNG warning new, or do you see that in Gaffer 1.4 too?
I would suggest trying to simplify everything down with the aim of getting the smallest repro for the problem. Along the way you might find the cause, but if not, you will hopefully have something small enough for us to look at.
It might also be worth running Gaffer with `LD_DEBUG=files` (assuming you're on Linux) to check for unwanted system Qt stuff getting loaded.
Cheers...
John