After selecting : Settings / Plugin settings from the menu,
The plugin settings window appears with the top item highlighted
If one directly clicks within the checkbox of any other item in the list, this one will not be selected but the top item will be.
One must first click outside the checkbox in the wished plugin field then click in the checkbox in order to select any plugin other than the first one.
Steps to Reproduce:
fixed in commit 63cff6c52a8ba90a32b4377834b40ca8a9e59ecd in porthole's git repository, master branch.