Thanks for the video, everything seemed to work just as yours did in the video, I disassembled the two shafts and they have all of their parts and no damaged circlips. I noticed a few things while disassembling though, one being a few gear dogs that seemed somewhat worn, the second being that third gear was stuck on the countershaft, it spun freely but got caught when pulling it off, the splines are slightly burred where the gear sits. I have quite a few pictures of anything else you may need to see to try and help diagnose this problem.