Potplayer opening with Angel Script command box

I’ve lately downloaded several videos that, when clicked to open in Potplayer (my default app), an ‘Angel Script’ command box appears at the top of the screen. If I ‘X’ the box shut, Potplayer also closes. If I minimize it, Potplayer carries on running.
But the oddest thing is that every line of subtitle dialogue is duplicated, one on top of the other, like so:
“Have you quit beating your wife?”
“Have you quit beating your wife?”
This is a PIA. Can someone tell me how to fix this, please?
PS: This has only happened with a couple of very recently made videos.