Stutter only with flight plan in FMC

Did anyone notice that heavy annoying stutter only appear when you have a plan active in FMC?

I did a test with A320 by FBW, I started a flight on rwy (any airport) and I did some turns on the airport without entering any flight plan, every thing was very smooth, as soon as I entered the flight plan in the FMGS the stutters were very obvious and annoying.

i9 - 10900k @ 5.1Ghz all cores
32 Gb Ram 3200Mhz DDR 4
GTX 1080 8Gb
250Gb NVMe for windows
512Gb NVMe just for FS2020