If it works in Safe Mode, a startup program or service is the culprit. Perform a clean boot to isolate it.
If you're seeing a alongside the message TransMac "could not access drive" - GitHub Gist transmac drive has been locked by another program hot
Sometimes the simplest way to beat the Windows Indexer is speed: Unplug the drive. Open TransMac as Administrator. Plug the drive in and immediately If it works in Safe Mode, a startup