4/speed issue

I had this issue with two "rebuilt" transmissions. Turns out the synchronizer drums in both transmissions where cracked/ broke. I never got to dissemble either of these transmissions in their locked up state to see what exactly what was occurring, my assumption was that the synchronizer ring was jamming in the drum.
When this would happen, the only way to get it out of second was to take a 5 lb sledge to the shift lever and pop it out.

This is probably a worst case scenario, but something I figured was worth sharing.