Found a problem during a project migration to 6.2.x and I successfully replicated the problem on a example case.

The problem goes as follows:

When I tried to create a widget with 

Qt::Popup | Qt::NoDropShadowWindowHint | Qt::FramelessWindowHint as window flags and this attributeflag Qt::WA_TranslucentBackground, using QGraphicsDropShadowEffect on this widget as well, I could at first see the popup with the correct behaviour, but trying to use the popup a second time and it didn't show up. If I pass my mouse/or click above where the popup was supposted to appear the popup components would show themselves. If I pass the mouse several times the graphic effects seems to apply everytime. I recorded a video and I will upload the test case for a better demonstration.

Also I received these messages during my test on the video:
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)
UpdateLayeredWindowIndirect failed for ptDst=(960, 340), size=(111x238), dirty=(131x257 -10, -8) (O parâmetro está incorreto.)

O parâmetro está incorreto = The parameter is incorrect. It is my system language to push out the message.

I tested this exact same code on 5.12.10 and it worked fine.