Something I observed since a very long time on my Mircosoft Surface Book 2 is now confirmed by Citrix Support:
Citrix HDX session may stop responding and hang when using the two-finger scroll on a touchpad. This was observed in certain machines running Windows 8 or 10 with receiver 4.10 or higher.
There is currently no solution, but the workaround to press a system keys like Alt-tab or windows key to wake up the OS input queue and automatically correct the problem.
Citrix and Microsoft is investigating the issue.
https://support.citrix.com/article/CTX236170
UPDATE 27th of October 2018
Microsoft has finally fixed the issue and published fixes for Windows 10 1709 and 1803:
Windows 10 1709: https://support.microsoft.com/en-us/help/4462932/windows-10-update-kb4462932
Windows 10 1803: https://support.microsoft.com/en-us/help/4462933
Marco Klose works as a Technical Consultant, Architect and CTO focused on Application & Desktop virtualization as well as application delivery with the Citrix product portfolio. He is specialized in Citrix virtualization, Citrix networking and Microsoft products. He has +10 years experience and holds the latest Citrix certifications and is member of the Citrix Partner Expert Council EMEA (PTEC). Since 2021 he is also a Citrix Technology Advocate (CTA).
Great find, keep up the good work!