Plasma dialogs (and others?) disappearing on wayland + Qt 5.13

Hey,
Since I switched to a Qt 5.13 build, I'm seeing that some dialogs
eventually stop showing up.

It happens randomly and I'm not even sure that it's Qt's fault
anymore, but I wouldn't discard it either. Initially I thought it
would be [1] but it got fixed and I still get it.

An easy way to trigger the problem is by using krunner. Just open it,
type something until you get some results, press Escape. Sometimes it
needs doing a couple of times.

With yakuake it can be done as well by pressing its key combination a
couple of times not even that quickly.

Any ideas what this could be?
Aleix

[1] https://bugreports.qt.io/browse/QTBUG-76124