I have a camera I'm working with over USB with MTP/PTP. Yesterday when I used a remote control application on my computer it was correctly interpreting the packets as USB-PTP and showing a lot of helpful information. Today, it is not recognizing them and there is no way I've found to "force" it. I've tried disabling everything in protocols except USB-PTP, the Decode As menu in the software, as well as starting Wireshark from the command line with wireshark --only-protocols usb-ptp.
I have a saved dump from yesterday that worked and one from today that is not working if it's helpful.