The Mint workaround almost worked for me. I am also on 20.04. I moved a file out of my target folder and into a new folder on the same level. The files in both folders became accessible. I moved the file back into the original folder and the folder became inaccessible again. When I try to move any files from my computer into the target folder, the folder once again becomes inaccessible. After a few minutes of nothing happening, I get the message, "Error While Copying: There was an error creating the folder "folder_to_transfer". File not found". After that, if I leave the folder and go back in, I can no longer access the files. I get the same error I originally did: "Location could not be displayed: Sorry, could not display contents of "target_folder": libmtp error: could not get object handles of [hex]"
The Mint workaround almost worked for me. I am also on 20.04. I moved a file out of my target folder and into a new folder on the same level. The files in both folders became accessible. I moved the file back into the original folder and the folder became inaccessible again. When I try to move any files from my computer into the target folder, the folder once again becomes inaccessible. After a few minutes of nothing happening, I get the message, "Error While Copying: There was an error creating the folder "folder_ to_transfer" . File not found". After that, if I leave the folder and go back in, I can no longer access the files. I get the same error I originally did: "Location could not be displayed: Sorry, could not display contents of "target_folder": libmtp error: could not get object handles of [hex]"