decklink 4k extreme few adobe bugs?

In after effect I can work with 4k comp and output to 1080p by checkbox the "scale and letterbox output to fit videomonitor" but this kills my 25p realtime playback to 10fps! If I uncheck it it becomes realtime again.

I have no 25p 1080p settings in ae. Only 24 and 23.976.

In after effect the preview has a pulsing motion. I dont se that on the computer screen. I tried with 1080p 24p alexa demofootage from bmd website (to get 24p footage since all mine is 25). Tried both 24p and 23.976 and matching comp settings.
Same clip in bmd "media express" and premiere playsback smooth.


I tried to go to the bmd settings and unched the "use 1080p not 1080psf" But that does not seam to help.

Thanks, after we fix this im a happy man!

joelarvidsson@gmail.com