What causes Invalid Shares on RVN? Unstable core or memory OC?

Hello, I understand well that on ETH, invalid shares are usually do to unstably high memory overclocks.

Since my memory overclocks are lower on RVN, it seems more likely invalids are caused by an unstably high core clock due to a low power limit. Is this usually the case? Haven't been able to find any good info on Google searches.

Thanks!