12.0 is quite old now, so it's worth trying with the current update (12.6) in case it improves things.
Toggling Preferences / Miscellaneous / Advanced: mtp_enable also helps with some Samsung phones. (If set to False, it won't disable MTP support entirely; it delegates more of the MTP handling to the Windows shell. That works better with some phones, although not all.)
Updating the OS on the phone sometimes helps as well, if it isn't already on the latest version available for it.