For a long time (years?) I've been struggling with copy/paste between two machines connected with Multiplicity KVM Pro.

Scenario 1

I often try to copy text or an image (via Windows + Shift + S) from my secondary machine (seamless mode) and paste it on the primary machine.  Usually this fails and the app I'm trying to paste into may go unresponsive for a while, perhaps about 30 seconds.  Well today I finally figured out the cause of that problem: Malwarebytes Premium.  Specifically the Ransomware Protection module.  Malwarebytes is only running on the primary machine.  Disabling the Ransomware Protection module works around the issue, but the better solution is to add an exclusion for the Stardock folder in Program Files (x86).  That also solves this issue.  Hooray!

Scenario 2

Unfortunately copying and pasting files between computers in seamless mode still does not work for me.  I've currently got Malwarebytes completely disabled and not running.  I've run the MPPortFix.bat file on both machines.  Windows Firewall is also disabled on both machines.  I've restarted multiplicity processes (via the context menu option on the tray icon) many times on both machines since it is the only way to clear the bad state once the clipboard transfer is broken.

When I try to copy a simple 1KB text file from the secondary to the primary, this dialog appears on the primary:

It clearly knows the name of the file I was trying to copy, but it never manages to accomplish the file transfer.  This simultaneously appears in the taskbar:

Sometimes the dialog just shows this:

Restarting the multiplicity services on the primary machine causes the dialog to close.

Anyone have any ideas, or additional troubleshooting steps?  I am an experienced software developer and not afraid to get my hands a little dirty to get file copy and paste working.