Comment 1 for bug 1733078

I can confirm this being the case in Mate 18.04 beta too. On mate community discussion it is said it is a bug in Plank iteself.

Here is the 18.04 report from Mate discussion https://ubuntu-mate.community/t/plank-annoyances-in-18-04-builds/16326

The same bug also appears if you launch an application that "closes" in tray, like psensor.
> 2) Same things for tray applications, e.g. I installed psensor which has a tray icon, if I minimize the psensor to tray it doesn't dissapear from dock.

Proposed solution: Add the possibility to configure "ignored applications". The applications marked as ignored will never show up in dock.