Strokes inside symbols don't show correctly when exported as a png

Here's a problem that I've noticed a number of times. It seems to happen intermittently and the really annoying thing is that it doesn't show up in Illustrator, only in exported images.

Strokes within symbols don't always display correctly when they are exported as a png. It seems to happen when the symbol is rotated or scaled. It doesn't always happen. I can't work out what specifically makes this happen or not happen.

I've attached a screengrab and a screen recording to show the process.

Artboard 1.png