Same probleme here on affinity 1.8.3.641 BUT what is very weird and annoying is that it worked perfectly fine few month ago, I could worked on 4096x4096 files, save same as tif , reopened the tif without any issues. now, i can't even open a 2048x2048 tif file....i will try to revert to 1.7.xxx to see if it's better but that's not great. It also crash on designer.
i didn't made any change to my PC
win10
i7-7820X
128GIG ram (so obvioulsy, not a ram issues)
1070 and 1080ti
Edit:
I unistalled Photo and reinstalled it, it worked as expected now. What is weird, i didn't reinstalled designer but it can now reopen the same files without crashing... anyway, if you run into this issue, try to reinstall might solve it.
