Test if the issue only happens at remote unit or not.

If it is, maybe it's because the quality of the cable which connect between the local and remote unit.

To avoid the interference, please use STP network cable and also remember to solder the grounding wire.

Please refer to the user manual of the KVM extender to get more information.

Besides, if the issue is skew, please use the low skew cable to solve the issue.

Below is the link of Aten low skew cat5e cable.

If the step doesn't solve the issue, please try other steps.