I think this is related to something limiting the number of allowed concurrent max inputs; I have not noticed it occur for this specific key combination, largely because I don't tend to use the keybind to switch perspective.

I have noticed this occur when trying to do other things, for instance emoting;

1. Walk forward and to the left/right, (W+A / W+D)

2. Attempt to point at something while walking

3. Observe that you cannot point

It could be the same check preventing you from changing perspective.

***EDIT:

I think I completely misunderstood your post sorry, you're saying that you can't change your camera direction, I replied as if you had typed "perspective." This comment is probably not relevant at all then.

I think perspective describes more what I meant though