Hello.
I've got some problems width my "new" (second hand baught) RX Vega 56 because since i built it in, all games are rendered at 144 fps (Afterburner and the ingame fps counter are say this) but i only see 30 fps. I got an Radeon R9 380 in my PC before (I still have it) and i never had such problems.
PC specs:
AMD FX 8350
16 GB DDR3 RAM
RX Vega 56
650 W Power supply
256 GB SSD
2 TB HDD
1 144hz 1920x1080 screen width Freesync
1 60hz 1366x768 screen widthout Freesync