This has never unexpectedly popped up for me, and I am also not aware of any other user reports.
The scenario where this is expected to appear is when clicking the “start interactive rendering” in VFB or in viewport button in the Corona Toolbar while IR is already running. If you can consistently reproduce it appearing in an unexpected scenario, please let us know the exact steps how to trigger it.
That happened to me long time ago, when I was testing a new version of Corona, and happened exactly as Marcin said, never happened again since I understand I was “re-rendering”, Im trying to remember if my PC was sluggish because of a big scene.
