Version 4.333 used on WoW Classic 3.4.0.45506

Happens quite often on my Mage when conjuring food/water - it will use the mana and instantly replenish in the bar but and not represent the real reduction in mana (no clearcasting proc up) - I will get not enough mana error when I still have 1k mana or so remaining when conjure is about 750 mana. Casting a spell where I have enough mana will properly update the mana bar.

Just tested it on PTR and since the default frames also show enough mana and the action bar shows the spell as ready i am sorry to say that this is a mage bug and not a bug of this addon.