Folders keep disappearing and reappearing on external hard drives

Disconnect all other external devices in case one of them is causing a problem. Several years ago I saw multiple people report this issue when they also had a Wacom tablet connected. I don't recall if this only affected Apple Silicon Macs, or if this was an OS issue with Monterey. Either way, disconnecting the Wacom tablet allowed the external drives to work fine. Even if you don't have a Wacom tablet, it is possible another device could cause the problem.

Try booting into Safe Mode to see if the drive behaves normally. If this works, then some third party installed software is interfering with the normal operation of macOS. If the drives are utilizing the NTFS file system and you are using a third party NTFS driver, then Safe Mode probably won't work since these drivers also change some macOS preference files to utilize the third party driver which blocks the built-in macOS read-only driver from even working even when the third party driver is disabled.

In addition if you have any of the following types of third party apps installed these can cause issues similar to yours:

• Antivirus apps
• Cleaning apps
• Security apps
• VPN apps
• Maintenance apps

If you do have any of these installed, please locate the developers uninstall instructions and please uninstall. Then restart the computer in Safe Mode and then restart normally.

Are you telling us that you are currently using Clean My Mac to help maintain your computer? If that is correct that is likely the cause of your problem. Most experienced users on these forums consider CMM as malware. CMM has a long history of causing similar issues with thousands of users and should never be installed. Mac OS does not need it nor does Mac OS benefit in any way by having it installed.

If you do have CMM installed, please uninstall per the developers directions and then restart the computer in Safe Mode and then restart normally and test again.