Executive summary / TL;DR:
Try doing a find & replace of "=" with "=". Yes, replace the equals sign with itself. For my scenario, it forced everything to update.
Background:
I frequently make formulas across multiple columns then concatenate them together. After doing such, I'll copy & paste them as values to extract my created formula. After this process, they're typically stuck displaying a formula, and not displaying a value, unless I enter the cell and press Enter. Pressing F2 & Enter repeatedly is not fun.