After more 1 000 000 (one million) views on forum for 1.5.0.x development versions... and 1.6.1.0, 1.6.3.0-dev versions A new stable version, UltraVNC 1.6.4.0 and UltraVNC SC 1.6.4.0 have been released: https://forum.uvnc.com/viewtopic.php?t=38095 Feedback is welcome
Actually, It looks like its in vncviewer.exe, not in the SC. I used the latest SC builder, and I also used an old SC, and both had the same error. Then I realized that I just installed UVNC 1.0. Opened the viewer in a hex editor, and searched for byb, and there it was.