Illuminatuion does not refund when critting twice in a row in quick succession

[MrSmithers]

I just experienced Illuminate not refunding mana when spamming Flash of Light and getting two crits in a row. Not entirely sure what the cause would be.

My best guess is that it could be related to the below issue, where in the mana is refunded for your currently casting spell.
#722
It could be that it flags the spell as already having received the mana refund, but that's one for investigating, and not for guessing :D

[MrSmithers]

Another example