Yesterday while playing with Diedo and 2 or 3 others on 2fort, map vote started and disappeared, server chose the map, server restarted with 2fort we all came back in and after a minute or 2 of playing the server just pulled everyone into spectate and wouldn't let us rejoin teams.
Regarding the latter issue (not being able to join teams):
If a map change doesn't fix it and a server restart isn't possible, you can try this command:
amx_cvar stb_on 0
This disables the team balancer, at least for the duration of the current map, or maybe until server restart.
If the issue returns after map change, you can also try:
amx_cvar stb_handle_auto_assign 0
This just affects pressing 5 (auto assign) in the team selection, but maybe this setting is kept when the map changes.