In Solidworks plugin, if there is a suppressed child item that is checked out, it will block the checkin of the parent item giving an error (screenshot attached).
Upchain should be capable of handling these checkins better. It is obvious that when a user is trying to checkin the parent, all checked out child items also should be checked in, even if it is suppressed. So the plugin should be capable of looking at such child items, initiate a checkin for the suppressed child item and then checkin the parent.