Had a similar issue on my 16' Z, except mine was the tach sticking. It only did it once and it went back to normal after turning the car off and on again. I still dropped it off at the dealership to see if anything may have been wrong but they couldn't replicate the problem and sent me on my way. It hasn't ever happened again though and that was about 10k miles ago.
There's a picture of it in my post.
Rpm gauge is way off for no reason??