RDS 2016 connection from WYSE ThinOS has slow screen paints

I'm testing a Server 2016 RDS environment and when using RDP with a WYSE client, the screen paints are very slow.  I've updated to the latest firmware I can find for our WYSE C10LE (8.3_014).

ICA connections to 2008 R2 with XenApp 6.5 are beautiful.

ICA connections to 2012 with XenApp 7.3 are beautiful.

RDP connections to 2008 R2 seem fine.

RDP connections to 2016 RDS VM on VMWare and a physical server (HP DL360 G7 which is the same model the XenApp environments run) both paint the screen at a pace that you can shake your head and keep time with.  (no performance issue is noticeable from a full Windows 10 PC)

I've tried firmware and I've read forums suggesting graphic settings or slow network is the cause, but our network is not slow.  I'm not willing to replace all the C10LE devices with more powerful thin clients, so I thought I'd check and see if any of you have another suggestion before I turn the RDS servers into XenApp 7.14.