Weapons not switching during mission?

[NovaXcaliber]

So I was on an Infested sabotage mission. A juggernaut spawned and kept taking my squad down cuz we were in a tight corridor. I died once, my squadmates were all down, and I was left to fight it until my squad revived or died. I had my secondary equipped at the time and tried switching to my main. Nothing happened. I tried a few more times before mashing the switch weapons button, but it still didn't work. I tried hitting the juggernaut with my melee, but that didn't work either. So I had to spend the rest of the mission unable to use anything but my secondary.

Then it happened again in another mission. Anybody else have this problem before?