Files shared at the folder level can re-trigger without a user re-sharing the file.
File collaboration can be updated from the parent folder. After the file rights are updated the file can trigger when re-scanned. This could cause confusion as the last action may not be the sharing of the file.
Response actions can remove collaboration at the file level but not the parent folder level. The scenario could cause the policy to trigger again because the folder has the permission.
Consider if the SaaS has the ability to block end users from adding collaborators to folders or consider a different response such as Quarantine.