I am trying to decide between
"may just have yet to upload" or "may just have not yet uploaded"
Is one preferable to another technically (not just opinion).
Neither is preferable, to be honest.
Simply, simplify, simplify. I suggest either
"It may have yet to upload."
Or,
"It may not have uploaded yet."
Sentence one sounds a bit hoity-toity. Sentence two sounds less snooty and would likely be more common in everyday parlance. The choice is yours.
VP
idiom has very restricted syntax. If you're not familiar with it, don't use it.