Transmission woes Options

[Joec]

Restoration finished on 1974 2.0 2 years ago. Car is totally done but couldn't get 4th or 5th gear on the transmission. Tried to no avail for months, researched, talked to many people but nothing worked so sent the car to a local Porsche shop. Their assessment after working on it including scoping it internally was the transmission had an internal problem. The transmission had been rebuilt by a shop in California and that shop said send it back and they would fix it. No easy task as I live in Vancouver, BC., but non the less sent it there and they apparently repaired it( never did tell us what they did). Got it back, installed it and now all gears but kept popping out of second. So back out it came and after examining it determined still not properly rebuilt so this time they rebuilt it. Took some time as parts had to come from Germany. Finally done and installed a week ago. Now back to the original problem of no 4th or 5th gear. So now the transmission needs to come back out and get taken apart again. This will be the 4th rebuild, is it possible they all missed something? should i just buy another transmission?

I am at wits end!!