I think if they are, you already know it.
They snap on the string with a light "snap" sound, without having to hold the string in place with your other hand to get it on there, they hold in place by themselves, but come off fairly easy, they don't make a noise when coming off at the shot.
The erratic flight, yup, but the only way I can think of to check that against any other reason is to alter or change nocks to make one fit well, then see if it affects the arrow flight.
You "can" alter the nock, by bending, sanding etc, and we used to do that in the past, but I believe today's nocks are a bit more delicate and doing that now might be hazardous to you, your bow, and anything nearby (if it breaks and causes a dry fire scenario).
Another scenario, if you are able ( it is not difficult) is to reserve the string using a smaller diameter serving thread, heck, even using left over Power Pro fishing line ( I have used 100# test before) will make things fit better.
Just change out one nock to make it fit "right", and see if it does anything at all different.
ChuckC