When you connect the player and device manager shows an error, uninstall the player in device manager, then disconnect the player and reconnect it. Hopefully Windows will reinstall it properly. If not, then uninstall the player in device manager, disconnect it, reboot the system, then reconnect it. Are you plugging the player directly into a rear usb port(not a hub) if you have a desktop, or plugging the computer in, then plugging it directly into a usb port(no hubs) if you have a notebook? If the player isn’t getting adequate power, or the usb cable length is too great(if you use a hub or usb extension cable) you might get problems like that. Did you try switching to a different usb cable? Make sure the contacts on the usb socket on the player aren’t dirty.
Perhaps you should try starting Windows Media Player after the player is connected, and close Windows Media Player before you disconnect the player. I remember that I had some problems when I connected or disconnected the player when Windows Media Player was open, and the player was in MTP mode. Since I don’t transfer protected files to my players, I don’t use Windows Media Player with them anymore, and use MSC mode and Windows Explorer copy and paste to transfer folders of songs to the players. I had all kinds of strange problems when I used MTP mode. MTP mode should be avoided unless you have protected files and must use it. It is best not to use Windows Media Player with your player(unless you have to since you have protected files that need to be transferred in MTP mode using a media player to transfer the licenses).
Is the usb mode of the player set to MTP(settings, system settings, usb mode)? If you don’t use protected files, then MSC mode is recommended, as it is least problematic. The pc will only show files on the player that were transferred in the same usb mode the player is set for now, so if you have MTP transferred files on the player and switch the usb mode to MSC, when you reconnect the player, the files on your player won’t show up on your pc. The way to solve this is to format the player using the player’s menu deleting all the songs from it, then with the player set to MSC mode connect the player and copy the files to it again.