Shifter locked-up (6 spd)

[driveslikejehu]

First time really driving the car was this track day. The only significant problem to arise was the shifter becoming stiffer and then locking in third gear.
It's a 2006 STi 6-speed btw
At the end of both sessions, I could feel it sort of tighten up- become more difficult to shift. Then after 2nd session and sitting for a few minutes it was locked into 3rd gear. The shift rod really seemed stuck, not like internal broken gear interference or something. Later inspection showed what might be new wear marks on the shift shaft.
shift shaft 1.jpg

Decided to have lunch, give up for the day and flog the Cayman for one session. After a couple of hours, I could shift normally enough to load it on the trailer. Next day seems normal. This all really makes it seem heat related.
Given that aluminum has twice the thermal expansion rate of steel, it’s kinda hard to see how the shaft could expand enough to seize up. But that’s what it looked like. Is it something deeper inside?

I loved to hear thoughts on this. I haven’t yet searched thru the forum for similar experiences.

Though it may not be relevant, my ZDB set-up never has felt great. Though it seems properly adjusted, it has always feels a bit “crunchy;” doesn’t smoothly go into gears. Maybe just worn synchros, but never sure if I have the cable/shift rod linkages adjusted properly. Might just be the 107,000 miles trans needing to be rebuilt.