Platform, device version and operating system:
Mobile - Android 9
Screenshot or image:
Screenshot not possible
What you were expecting to happen, and what actually happened:
I expected to get mana from matching similar colored gems and I did not get any mana.
How often does this happen? When did it begin happening?
This can occur multiple times in a single battle and in any battle type. It has been a part of the game since I started play and I thought it was a game mechanic. But when it started costing me victories I researched it.
Steps to make it happen again
All I have to do is play a battle. It will happen though I have not seen a trigger for it to occur. It does not seem to be based on the troops current mana, the time spent in the battle or how many gems are matched.