You know it might be my X700 that gets fast or loses “last check” when it’s low on battery. Because just today the battery needed changing.
After that a roll of TMX at box speed came out perfect.
I still will give TMY @ 800 half a minute more though.
It could be that indeed. My X700 gets a bit funky on low batteries too. That said I have had trouble figuring out both TMY and Delta 400. I can't seem to get the exposure/time down to the point I will probably end up doing some basic film tests for those. TMX though, always seems to come out wonderfully in XT3 (as does HP5, CHS, and really most other films).