Hi Benjamin,
Thank you for the question and I am sorry about the issue!
This turned out to be a new defect with Archicad 24. Unfortunately, we do not have any workaround for this rather than turning off the Selection Highlight altogether (which is not very ideal). We registered it as defect DEF-1774.
Thank you very much for spotting this bug, and I am sorry for the inconvenience! If you have any further questions, feel free to ask me again!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT