T5 Transmission - Stuck in 3rd After Top Cover Reseal - Fix without Teardown?

Looking for some experienced input on a T5 issue that showed up after a simple reseal.

I’ve got a T5 out of the car and open on the bench. The transmission was working perfectly prior to this. The only reason we opened it up was to fix a leak at the top cover, we measured about a 0.23 mm gap on the top right corner of the cover.

Important point:
We did NOT remove or intentionally disturb the geartrain, synchros, or mainshaft assemblies. This was strictly a top cover reseal.

After reassembly, here’s what’s happening:

Transmission binds and gets stuck in 3rd gear
With the case open, I can see that one of the synchro hub keys/struts is out of place
The synchro sleeve is not centered properly over the hub
It appears to be the 3rd/4th synchro assembly

From visual inspection:

At least one key has popped out
Concern that the internal synchro spring is no longer seated correctly
Sleeve position looks off, which lines up with the binding in 3rd

Questions for anyone who’s dealt with this:

• Can the key/strut be carefully tapped back into place and the synchro sleeve re-centered without pulling the mainshaft apart?
• Does the sleeve need to sit perfectly centered over the hub at rest, or is slight offset normal?
• If a key has popped out, is it safe to assume the internal spring has also shifted or come out of its groove?
• With the gear stack still assembled in the case, is there any realistic way to access and reseat the synchro spring?
• Or is this realistically a full teardown situation where the mainshaft has to come out and the 3/4 synchro hub needs to be rebuilt correctly?

I’m trying to avoid tearing the whole thing down if there’s a safe way to correct it in place, but I also don’t want to force anything and risk damaging the hub, sleeve, or blocker rings.

Appreciate any insight, especially from someone who’s dealt with T5 synchro keys popping out like this.

Attachment 228299

Attachment 228300

This is a Dropbox link with all the photos and the leaking top cover: https://www.dropbox.com/scl/fo/di1j4...=w6kifm5p&dl=0

My guess is you didn't have the shift plate/forks in the correct orientation and upon installing, missed where it was suppose to go, and when you shifted, jammed it. To answer your question, best thing is to take the mainshaft out and fix it right. It's not a complete teardown, but you'll need to remove the tailshaft and 5th gear assy. as well as front end. The snap ring(s) that support the "keys" may be out of place and trying to "guess" while in the shape now, is a risk.