Hello David,
Sorry for the inconvenience this issue is causing.
To ensure the deleted fields are completely removed, please also check and empty your Trash. In some instances, items remaining in the Trash can still appear as selectable options in dynamic collections. You can access the Trash here: https://prnt.sc/lwxuZg-nKa7u
We understand this behavior isn't ideal. We've already notified our development team about the issue, and they will be working on improvements in a future update.
We appreciate your patience and understanding.
Best regards