I am using MATE Dock Applet v.80 (GTK2) on Ubuntu 16.04 LTS with the Mate desktop. It works fine, but for some programs the wrong application icons appear, which is quite confusing.
For example, the application TagSpaces (see: http://www.tagspaces.org) shows the icon of PyChess. When opening the context menu for this application, all entries are labelled with "PyChess". The program TagSpaces is a portable version, so no installation was necessary.
What can I do to fix this issue?