Hi, I am experiencing the same issue. When I try to select hosts in the group memebership tabs and remove them from group or get to the hostpreferences a different host is edited. On mouse-over the hyperlink of the host has a different id in it. It looks like the id variable is incremented by one or maybe it is an issue caused by a loop in the source which runs one more time than it should.
My further investigation showed:
If I create a new group an edit memberships (delete, select host for editing preferences) everything works as it should(the host-id in the hyperlink is correct) as long as the server is not rebooted.
By the way when in the hoststab itself the hostids are correct, the incrementation happens only if i switch to the grouptab.
I am runnning ubuntu 16.04 with fog 1.5.2 and php7. The only changes i did to the clean fog-setup, were:

Editing the fog vhost configuration(Moving </Directory> Tag) and setiing a different php-fpm max_children count higher to get rid of the Updating database error 503 after multicast-deploy. I don’t think there is some connection between my changes and the webguibug.

Please excuse my bad English, I hope this information helps to target the problem.