comments:
You can pull the transmission and clean the forks if you wanted. That is technically better. It's a lot of work though. You mentioned you don't have any more money but if you were going to pull the trans and clean it you might as well try and get a clutch set and replace the clutch. It is about $800. The drilling to clean is to avoid pulling the transmission since it sucks to do. THis is the Luk clutch kit. Luk makes the OEM one so it's identical. There is no better one so replacing with OEM or the same maker as OEM is best. https://www.amazon.com/07-233-LuK-Quality-Replacement-Clutch/dp/B07L9W1RVV There are cheaper ones on amazon and available. Avoid them. They are almost always just OEM clutches pulled from cars and cleaned really well and sold as new. Sometimes you might get lucky and get a good one but a lot of the time they are bad and will fail quickly. Also. One thing you can try that might help a bit is to stop on an onramp for a highway when it's safe to do so then floor it to get to 60-80mph as quickly as possible. Do it a couple times. The fast shifts can clean up the forks a bit and might help.
The TCM is probably fine. There is a grounding issue you could try. it won't fix a stuck clutch but it ensure the TCM is working properly. The 2017 has the newest TCM which isn't known to fail. Here is how to do the grounding fix: https://www.youtube.com/watch?v=oVzAQDOLtiY If clutch B is stuck it's because the forks are caked in clutch dust. It's a common problem with this transmission. The fix is a clutch job. It can be done with no special tools but the clutch pack is about $800 if it's DIY. A shop will charge $3-4k. If your brother is able to swap the transmissions, he will mbe able to do a clutch job since the hardest part is removing the transmission. This is the clutch to buy. Luk makes the OEM ones for ford so it's identical to an OEM one. https://www.amazon.com/07-233-LuK-Quality-Replacement-Clutch/dp/B07L9W1RVV Here is the guide on how to replace the clutch once the transmission is out. https://www.youtube.com/watch?v=EIJt9anfdSM