Hi One reason can be the touch setup -- Can you please explain a little more on this? Well since it only happens sometimes, i guess its not that. I have seen something like it when touch was setup for gestures and you kinda moved the finger when you "clicked" it would then start the gesture and sort of eat the click. Could also be a bug in Qt4.8 that the later fixed with Grabmouse -- Is there any defect ID that you remember? That will add more waitage for the understanding. Sorry nope. it was a duck. It was due to calling a message box that would run event loop and button would not redraw before after. One of the other thought that I have is, if this is really a UI issue or this is being a side effect due to any other -problems such as CPU load, Memory full, etc. Do you think it is possible? Yes that is really possible if the target is low powered board and it's low on say ram then the same task might suddenly take much longer and the button will appear down. Have you tested with a button that does nothing and see if that can get stuck?

@jsulm Sorry for the late response. Thank you very much for very clear answer. It helps.

Its something completely custom. It does not have package manager.

Do you have Qt configured to use that display ?

Figured it out. The 'mark as solved' option is there for people with admin rights, as the functionality relies on the admin 'rename post' function. For a thread OP to mark a post, he/she needs to add [solved] to the title. I'll take a look at the plugin that adds the thread tool option to see if it could work with normal OP rights too.