Hi,

Here are some things to check:

1. QuickBooks Online often ties project dates (START and END) to the status or progress of the project. If the project is still marked as Active or in any status that depends on those dates, QuickBooks might automatically reset them.
2. Some fields in QuickBooks Online can't be permanently deleted because they are part of system templates. These fields might be locked until the project is in a certain status, like Completed.
3. Since you've tried clearing the cache and using incognito mode, it’s worth trying a different browser or device just to rule out any session-related issues.
4. If you're dealing with custom date fields or third-party integrations, those dates might be required by the system or integration, even if the project is marked as complete or inactive.