Every-line Composer bug - text shifts when moving text frame

I just set some text in the latest verision of AI (27.7) and noticed that when I'm moving my text frame the text inside it moves out of sync with the frame. I haven't seen this before today (but I do generally do all my typesetting in InDesign which doesn't behave badly like this.)

I've tested it with multiple fonts, incuding system fonts. Same outcome.

What stops this strange behaviour is when I click the node on the middle right of the text frame (that coverts a text frame to the 'other text thing' — I can't remember what you call this, it's got an arrow and a T…).

Screen recording attached to this post for your convnience.

Thanks!