If you're ever unsure, call up your local office during normal business hours 8:30-4:30 and ask. They are not "primary control surfaces", according to the Gardena NTSB office, but it is not in writing.
The NTSB does NOT want to do any more paperwork than they already have and with a 2-3 year backlog on their current accidents, if the problem isn't major (i.e. 121 airliner with passengers aboard), they will tell you it doesn't need a report. If you don't make the call and ask, there are untold consequences, especially if the aircraft later crashes.
Calling the NTSB directly does not involve the FAA. The NTSB wants credit for solving whatever safety problem versus the FAA taking credit, so reports are not automatically forwarded. If you call the FAA Regional Operations Center because it's an item requiring an immediate report and after hours, the FAA will involve themselves including listening in to your conversation with the NTSB. If you do have to call, tell the duty officer that you need a call back from the NTSB.
There are plenty of consequences for making the phone call. Your mechanic, employer, coworkers, and others may shun you. You may have to find different ones of all of the above, if you can. There is a general phobia in aviation about involving the NTSB, definitely deserved.
But it beats seeing the wreckage of the plane you had a problem with on the evening news having killed people, and you didn't report the initial problem. It gets worse, you can bet you'll be on the witness stand trying to defend why you didn't call, when whatever problem 'obviously' (to greedy/grieving widow attorney logic) caused the accident.