Weapon rests during combat

[Tawnea]

I seem to have an issue with my weapon trying to rest (going out of battle mode) every couple of minutes during battle with bosses when solo inside dungeons.  I have been soloing The Pigtsy and everytime I do it happens during both boss fights.  Happens in both stances, randomly.  This has also happened in the Spider dungeon so it doesn't seem to be related to Pigtsy.  Anyone else had this issue?

 

Blademaster -  Yehara