Invisible EXP bar

During duties, my EXP bar becomes invisible and I can't check my levelling progress.
It happened today and yesterday, in the following instances:
- Sastasha Seagrot
- Halatali
- The Bowl of Embers (Hard)
- The Navel (Hard)
- The Binding Coil of Bahamut (turn 1)
- The Binding Coil of Bahamut (turn 2)
All I know is that the bar just vanishes, and when I go to the HUD layout settings the EXP bar positioning is where it should be, but the bar isn't there.
I know it's not a big issue, but it's very annoying.
Thank you in advance.