Game version 31.0.6. This occurred at S3.23.2, when enemy dies they do 100% damage. I had Aegir going off, send a bunch of tiles at enemy and did some cascading damage, and the damage also healed me so there was an overload of damage text display on screen. After it’s all said and done, there was a line of text remained. The visual bug is possibly triggered by too many lines of damage being displayed. Once it’s there it stayed for the rest of the level.
Ok I got this same bug again and I got a video showing the aftermath.