Thanks for the reply @UnfadingShimmy. I did read the xbox support article about power cycling your console and will see if anything changes after the 72 hour window.
What I don't understand is how I'm at 77%. Prior to sitting down to "complete" the Tall Tale, I either had 1 or 2 more runs to complete before reaching the 5/5 tall tale completion threshold (I honestly can't remember how many I had left). Prior to that day--which was about 3 weeks ago BTW-- I had found all journals and completed the Tall Tale 3-4 times.
None of the math I'm doing comes out to 77% so I'm wondering if this problem started before I noticed it.