Camera bug: it switches to 3rd-person view for no reason

I've got this bug for several times on different maps when  my camera suddenly switсhed to 3rd person mode and I couldnt switch it back to 1st person mode.  I still could move, switch weapons and shoot, but the camera was fixed to the point whre it happened. After I was killed and respawned camera switched back to 1st person view.   I'm not sure what actually caused it. The last time I've got this bug when I stepped into a crater near the destroyed tank.