Cast when Damage Taken levelling up without me clicking it

I thought I was going crazy, but this gem has levelled up from 1-4 on its own. On it's first level, I right-clicked the + button to hide the prompt (like I did for my Molten Shell and Flame dash gem as shown). However, occasionally, when I enter a map, the gem pops up prompting for the next level. I noticed that it has leveled up and has accumulated experience for the following level. I hid it again the same way, double checked that it did not level up (still showed the prompt when I opened my inventory) and continued on.

After it happening three times, only with this one gem, I'm fairly certain it's a bug. Note that the gem is Corrupted 23% quality.