I've noticed the popup "toasts" (as they're called in Android)
often sometimes** do not disappear until closed with the [X] at the right end of the box. Perhaps because they're generated by a QDP panel that has been closed, and the toast is over the main page. I haven't observed enough to notice a pattern. It's an annoyance mostly when making training videos and I have to close them manually, then edit out the action to save time.
I'll start "timing" myself to see if I'm closing them before 5 seconds has lapsed. My recollection is that some stay present for a minute or more.
Also using Chrome, version
78.0.3904.108 . ** I just did a couple of random tests, the toasts fade out within five seconds. I'll have to capture an instance when they don't.