X301 with USB Ehanced Port Replicator Screen Freezes

[Nifill]

I recently started using X301 with 4GB mem, 128GB SSD and USB Enh Port Repl.
I use the Port Repl to drive a 17" LCD screen and external Keyboard.
I find that with the X301 screen extended to the external display, I get occasional cursor freezing for approx 1 or 2 secs under heavy workload.
When I disable screen extension and run just using the X301 display everything seems fine.

Anyone have this experience ?

Nigel