it seems such an issue occurs only for “custom floating window” session type and Windows client display set to 16 bit depth (that is often the case when the Windows client is reached by Windows Remote Desktop).
Following on from my previous message. I’ve managed to get someone else to to try connecting the remote Linux application not through a Remote Desktop via a VM and everything looks and responds fine using the NM desktop client.
I’m still unsure why this is an issue via a Remote Desktop using a VM. I’ll get the hypervisor details you requested and post back.
Yes, the issue seems to occur when using a ‘custom floating window’ with the default 16bit depth of a Remote Windows Desktop. In my case this is being run in a VM and accessed via Apache Guacamole using a Mac (but the same issues happens when access the RDP using a windows laptop, not using Guacamole).