WTware RDP client

hello,
we are evaluating vtware in our environment, where we actually have a windows 2012 r2 terminal server and some windows 10 virtual client.
Everything is ok except that sometimes some strange artifacts appear on the screen, please check the attachment for an example.
we are using raspberry pi 3 model b.

Please, make a log: https://wtware.com/logs.html

Can you clean artifact with mouse pointer?

hello and sorry for the late reply,
if I try to clean the artifact with mouse pointer sometimes the artifact disappera but sometimes it keep remaining on the screen.
I have also antother strange problem, sometimes (about one time/day) the terminal freezes completely for some seconds.
I attach the log. thank you in advice

"Not enough data in stream in rdpclient-gfx-rfx-tile-decoder.cpp line 1081." in log is strange. We have never seen such RDP before.

Did you change something in server policies near this location? https://wtware.com/win/nla.html

Install updates on server. If errors still appears, tell me, what are you doing when terminal write this error. It's graphic issue. Something unusual displayed this time.

hello,
we havn't change server policies as indicated.
the server is updated.
but soon we will try wtware on another server and i'll let you know if the problem persist thx