Hi, found this bug in game, it is very easy to reproduce:
With Harmonious Mantras you get 3 charges for every Mantra. If you get downed, any Mantra that was at 3 charges loses 1 charge, so if you rally you will have them at 2 charges.
This only happens with mantras at 3 charges. If they were at 2 or 1 charge when you get downed, they will remain the same when you rally.