strange pink border

I have recently got a new Macbook Pro M4 and loaded the latest Adobe suite 2025, previously using 2023, didn't get round to updating.

I have a number of strange things happening, which seems to be when opening my older created Illustrator files. One shows a completely white page, no content, until I zoom in or out then the document appears. And another where a thick pink line appears at the bottom and right of the window, screenshot attached.

Is this a bug? I'm thinking of backdating to 2024 version to see if that helps.