Seems that sometimes and for some reason, the "next wave" counter wont start, or trigger, and you will miss the next spawn wave leaving you stuck in spectator mode until you switch classes and switch back again.
I don't know why this happens, but I get this issue fairly regularly.

Yeah a friend of mine has that problem too.
For some reason he didn´t spawn 3 times in row. He had to watch all the time.
Then he added a gas mask to his loadout and after that he could spawn with the next wave again.
So the loadout seems to affect the spawn.

I personally never encountered such a problem.

Confirm this have happened to me and 2 friends aswell.
From what i remember, i didnt change loadout before or after it happened.