Cannot set the checkboxes on Plugins-System Events

When attempting to set the System Events checkboxes for Plugins (new or existing plugin), the checkboxes do not hold their state. In other words, if a box is checked and saved, it is not checked on its next edit.

Further, if a new box is checked with other checked boxes already in place, this will wipe out all checkboxes to be unchecked.

Example:
Go to an existing plugin (TinyMCE in this example) and simply uncheck one currently checked box, press Save and recheck its System Events. Note that the checkbox you unchecked is fine as is the other currently checked boxes.

Now check an empty box and take note of the boxes already checked. Press Save and recheck the System Events. Note that all boxes are empty and TinyMCE no longer appears in document editing.

I tried this on a fresh, non-edited install of version 9.6.1p2 with root login to the db on an IIS server.