Fluctuating base clock causes frame dips?

I've been trying to diagnose why I have these massive frame dips, and through Afterburner, I have found that although at 100% usage, my GPU's base clock is fluctuating from 1100mhz to 300mhz. This only happens in Unturned and CMS 18. Is there a way to lock the voltage in place? Any help is much appreciated.

CPU: AMD A10 7870K

GPU: RX 460 (Sapphire)

I can put the rest if someone needs it, I didn't think it was necessary to include.

UPDATE: Radeon Wattman says the frequency stays consistent but the load bounces between 0 and 100%. Afterburner says the opposite, the load is 100% but the frequency bounces between max and 300mhz.