Since Blender 3.1+ any file that ends with 4 digits and a separator ( e.g. _1280 ) is by default interpreted as UDIM, and subsequently fails to load in eevee / the viewport ( pink shader ). It still renders fine in cycles, at least until you change the type to single image and back to UDIM. Which are bugs I assume?
The bugs aside, this seems to be a deliberate decision to interpret any 4 digits as UDIM, which is i think problematic, as many files have endings like that - e.g. resolution, date, frame number etc.
UDIMs are a special case, not the norm. As such the ‘detect UDIMs’ toggle in the image loader dialog should be off by default.
It is not a bug to have an image interpreted as UDIMs if user choice of source is UDIM tiles instead of Single Image.
“detect UDIMs” toggle enabled is just a default that does not suits your workflow.
Maybe having texture files with 4 digits is not the norm, either.
Currently, you can choose what toggles are enabled in keymap configuration as settings for Alt O shortcut.
It’s more of a systematic problem. Blender does very dumb thing where it simply throws away file open dialog settings after a session. It never saves them. So customizing and file load setting is just not possible. This means that whenever there is a poor default setting anywhere in the file loading dialog, such as bad decision to make UDIM detection enabled by default, you have no other choice than bash your head against the table every time you make a mistake.
Poor defaults are bad. Poor defaults in system where defaults can’t be changed and saved are very bad
I never said it is a bug, but bugs are in its implementation. However - while my workflow is adaptive and I can accommodate this if necessary, there are many people, and many people i teach blender, where this behavior leads to confusion.
Mainly because I can’t name any software - in any field - that does that kind of interpretation on load by default. The one and only is maybe to detect image sequences in video editors, and even there I would rather have it not do this by default.
I think in a so specialized case as UDIMs are, this is a very uninformed decision.