On Qt 5.12.11 (MSVC 2017), this bug doesn't exist, so there's clearly a code regression after this version, between it and the 5.15.0 (MSVC 2019) according to my tests.

Otherwise, on the Qt 5.12.11 (MSVC 2017) version, this other bug that I reported doesn't also exist : QTBUG-101874

I talked about this bug here : https://forum.qt.io/topic/138099/infinite-wait-when-stopping-qthread-event-loop-and-then-calling-wait you will notice that the participants are in disbelief despite my efforts but the bug is there and I'm 100% sure.

Here's how reproduce this bug :

1. Clone this github repository : https://github.com/embeddedmz/QTableViewAdjustPolicyNotWorkingProperly
2. Open the CMakeLists.txt with Qt Creator, build, run the program.
3. Click on "Start", then on "Stop"
4. On Qt 5.12.11 the UI will return responsive after 10 seconds but on version >= 5.15.0 the UI will never return responsive.

Description of the bug : when quit() is called on the QThread object it stops the this last's event loop but then this last gets restarted when processEvents is called on the QThread's dispatcher. Result : when the main thread calls wait(), it will wait undefinitely.