Fatal error: Class 'Group Membership' not found in ginvite.module

Wamp 3.6x
Apache 2.4.23
Php 5.6.25
Drupal 7.5.4
Ctools 7x1.2
Panels 7x3.9

I set the issue to "normal" instead of "major" since the steps to reproduce shouldn't be too common to affect a large group - but it is rather severe never the less since the bug leaves the site (temporarily) inaccessible and renders panels in regard to groups (once the bug occurs) utterly useless

Steps to reproduce
Install Group, Group node and Group Invite
Add a group
Go to panels -> Group -> Selection rules (for Variant) -> Query string (of url) -> add

---------------------------------------------------Modal Window error:
An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: http://boonyai.final/ctools/context/ajax/access/add/page_manager_task_ha...
StatusText: OK
ResponseText:
( ! ) Fatal error: Class 'GroupMembership' not found in F:\wamp64\www\boonyai_final\sites\all\modules\group\modules\ginvite\ginvite.module on line 81
Call Stack
#TimeMemoryFunctionLocation
10.0010315296{main}( )...\index.php:0
20.0010339184drupal_bootstrap( )...\index.php:20
30.04601150240_drupal_bootstrap_full( )...\bootstrap.inc:2533
43.78425233488module_invoke_all( )...\common.inc:5310
53.79725320328call_user_func_array:{F:\wamp64\www\boonyai_final\includes\module.inc:957}
( )...\module.inc:957
63.79725320592ginvite_init( )...\module.inc:957

---------------------------------------------------Try to disable ginvite to get your query string access back (admin/modules)
Fatal error: Class 'GroupMembership' not found in F:\wamp64\www\boonyai_final\sites\all\modules\group\modules\ginvite\ginvite.module on line 81
Same error returned on every page I tried to access after that

---------------------------------------------------Disable from Database to gain access to your site again.
Run Cron and flush caches

---------------------------------------------------Site is accessible again but shows
Warning: require_once(F:\wamp64\www\boonyai_final/sites/all/modules/design_structure/group/plugins/page_manager/tasks/group_view.inc): failed to open stream: No such file or directory in ctools_plugin_get_function() (line 785 of F:\wamp64\www\boonyai_final\sites\all\modules\essentials\ctools\includes\plugins.inc).

---------------------------------------------------Go Back to Panels->Group(edit) to check if the problem is resolved
Fatal error: require_once(): Failed opening required 'F:\wamp64\www\boonyai_final/sites/all/modules/design_structure/group/plugins/page_manager/tasks/group_view.inc' (include_path='.;C:\php\pear') in F:\wamp64\www\boonyai_final\sites\all\modules\essentials\ctools\includes\plugins.inc on line 785

Other panels are accessible again - editing group panel has become impossible

---------------------------------------------------remark:
I have yet to try to uninstall ginvite...
but I don't have any usable backup available since the site had a lot of empty rows which couldn't be exported that easily, so I am rather reluctant to take my chances on that at the moment^^, but I will report back on that (uninstall/db update script) once I am confident to have a reliable backup.

---------------------------------------------------Background.
Simply trying to make panels take over group add and edit forms

---------------------------------------------------p.s.
after seen this issue Error when unistalling group invite I replaced all beta 6 files with .dev only difference to the above is being asked to run db update script so I reverted the files to beta6

Well hope the info is complete^^

Good Luck to all ;)