It's the same root cause as in
https://forum.tixati.com/support/6343?p=3 - "Moving / Dragging Windows Abnormally Slow since a Few Months Ago"
Tixati's networking is momentarily blocked while its windows are being updated and rendered. One of the Windows updates slowed down text rendering substantially. In other words, this problem doesn't exist on Linux or older Windows. Fundamentally it's due to a slow CPU (single-thread performance) and how Tixati was programmed. If a window takes too long to render, there'll be no time left for Tixati to process network transfers.