Customizable speed is not frame accurate.

[holovicc]

With 4.4 a new great feature arrived, allowing smooth video output on 50 and 60Hz. Huge improvement, but it is not perfect. Regardless whether you lock it into 50 or 60Hz, the emulation will hiccup every once in a while (eg. goes smooth for seconds, then it shakes a little, then goes smooth for a while and the pattern keeps repeating). Tested on Eizo CS2740 and the new 16" M1 Max Macbook pro, both supports 50 and 60Hz, both produced the same result.