If I reset the columns on a folder to the defaults, and I then turn off the Type column and save as a default all well and good. I then go into my Skydrive folder (top level) and turn on the availability column and then choose to save the format for that lister and all below. Again all looks good.
Then I can guarantee without making any changes at all to DO the Type column reappears within 24 hours or so. I reset and go through the above again and it'll be fine again for a few days.
Weird and nothing I can find seems to trigger it. Thought it worth a mention to see if anyone else has noticed similar.
That could happen due to other automatic columns interferring with your setup. You could compare the active folder formats, which might possibly trigger this behavior,
by hovering over the lock icon at the bottom left, if you didn't already.
I can't think of anything that would cause that... If I were you, I would start with:
when things are working right, check the status bar format lock and write down how Opus is deriving the current folder format
save off an OCB
when things go wrong, check the status bar format lock again and note if how Opus is deriving the current folder format has changed in some way (i.e. that it's not your format definitions themselves changing, but rather if how Opus is determining which format to apply has changed for some reason)
save off another OCB
extract and compare the OCB's just to be sure WHAT is actually changing...