Render artefacts in MRQ // Possible FPS related?

hey there,

I´m constantly getting render artefacts with MRQ and haven´t been able to quite pin point the cause or the solution.
On some frames I get something like a flash with some object outlines in it (see screenshot).
I had it fixed at some point with lowering triplanar sharpness on a material instance, but it also occured on other renders without any triplanar materials in it.
I though it had to do with exponential heightfog, but it also occurred when disabling it.
My current workaround is to pinpoint the exact frames it happens on and then rerender them with slightly different subsample settings (1/12 instead of 1/8) for example.

Is it possibly an issue with the fps of the sequence being at 25fps, when subsamples are 1/8 (or multiples of 2)?