This is kind of difficult to explain, so I'll try my best.
As expected, using the xp tokens from gold daily dice rolls gives you xp, but at the same time your xp bar turns blue, as though you're banking experience over level.
It's not a problem at first, but at levels 7+ it's preventing me from using experience stones.
Step by step repro:
0: Make a golden daily dice roll.
1: at level 1 use an experience token (you now have a blue xp bar permanently.)
2: level to 2.
3: acquire xp to level to 7.
4: try to use a bigby's xp stone, you can't.
5: level to 8
6: try to use an ottos xp stone, you can't.
For further testing,
I tried using an xp token small enough to prevent me from leveling, theoretically avoiding a blue xp bar. It doesn't matter, the moment I use an xp token the bar turns blue and seems to stay that way no matter what.
It also doesn't matter if someone else uses the xp stone on you, same problem, you won't get any experience from the stone.