everytime i connect i device to my computer with spacedesk and i use my instant replay, the video of the instant replay just start blinking and breaking up
Yes, this is currently a known incompatibility issue with spacedesk.
If any screen recording/in-game replay from AMD or Nvidia is enabled, spacedesk will not work properly and you will probably observed a screen flickering for a few times.
For now, we suggest to turn off this feature before connecting spacedesk.