Hi Michael!
Finally I got my replies ready for you 🙂
Intermittent Bug With Number of Search Result Columns (Cards)
Unfortunately no, and there are no other reports of it either for some reason. May I ask which browser are you testing this on, and your screen resolution? Thank you!
Featured Image Source Size Not Working in All Situations
Looking at the source, this is going to be an issue with the plugin code. I see it is missing the cache section. I will fix this for the upcoming release.
Attachment Search / Filter for Default Post-Format
I do understand, and the issue is that that term does not actually exist – and it messes up the whole logic. If you think about it, the search is instructed to exclude items that does not belong to any of the taxonomy terms, but again somehow include the ones that does not belong anywhere either. There is no way of having both within a single query. This feature is something I have to maintain (single query), as adding/removing results after the completed query (within the core) would be a complete disaster.
I think the only possible option left is to simply remove the undesired results from the list. That I was trying to avoid, but I don’t think there is any other way at this point: