Hi I was looking to get some wisdom

For some reason I can't get into 5th gear , I speculate a broken synchro, whatever that is OR a broken gear? I have no idea , help!

It's driving me crazy having to remember to skip 5th.

What should I do? Is there another tougher transmission I could swap in here? Ap2 trans?
Any advice or suggestions ?

i know 800whp s2000's running the stock trans, it's a solid trans. I would either get another trans (AP2 is a little better) or just fix that trans for a few hundred dollars. *shameless plug* I can fix it if you're in SoCal, I'm a Honda Master Technician/ASE Master Technician.