I am experiencing rather annoying lag (delay) while changing Course, Speed, Altitude, V/S

I did monitor CPU/GPU and HDD load while changing MCP values and there was no noticeable load variation.
Honestly I do not know where to star analysing and solving the problem.
Maybe i can get some tips/hints on this forum?

Simulator: P3D v4.5
Aircraft: PMDG 738 NGXu
Windows 10 Home
Have fun
