How to fix? FPS vs movement on client-side vs server.

Dear sirs, good day!
Well a very simple question. We have a gameserver based on java, we’ve connected our ue4"client" (well by the rules we can’t change a gameserver).

And everything seemed fine animation of character, animation of mobs, movement, but when we’ve started to fill our server with trees grass etc, optimized it as possible (lowered everything we’ve got good and stable 50fps at full streaming world at the epic settings), very strange thing has happened! Character went crazy. When we have 80-90fps it moves like lightning and when i get heavy 40fps at 4k it moves SO SLOW, that my old granny is much faster than that (and i’m talkin not just about animation of that is happenning), but the real coordianates and speed differs very much from server.
So if you have 90 fps you click to run 100m and when it’s done in client we push stop, then play, and character is situated in the middle of the way that we clicked to run bout 60-70meters by fact on server. Okay…
30 fps - click 100m - we’re running half distance - stop - play we’re at the end of line of 100m… Q_Q it’s like a slomo
We’ve broke our head twice crashing a table…

  1. help! 8)
  2. is it possible to make internal tick timer that is not connected to physical-draw core? (cuz we need only gravity and particles)
  3. is there any settings that could disable connection between movement character component and a real-time phys-draw rendering of ue 4, then connect it to the server stats speed from server packs? That our character even at 10 fps could run properly at proper time +/- 1%, and YES that’s okay if frames will be skipped.

With respect. Please help.