Adding a group for the first time crashes because of incorrect field definitions

Could this be the same issue as this:

Problem

Fatal error when adding a Group for first time.

Fatal error: Call to a member function label() on a non-object in /***/sites/default/modules/group/src/Plugin/GroupContentEnablerBase.php on line 129

Occurs at least with these Drupal versions:
8.0.7-dev (the one simplytest.me is currently installing by default)
8.1.1 (local Acquia Dev Desktop)
The same fatal error in both cases, haven't tested other Drupal versions yet.

To replicate

Install Group in a fresh Drupal environment
for example https://simplytest.me/project/group

enable modules:

• Group
• Group Node

Rebuild permissions

Create a group type
Create a group of the type you created

Workaround solution

not completely sure about this yet, but clearing cache at some point after rebuilding permissions seems to help.

Update: testing patch (revert code), will report results

Tested 8.x-1.0-alpha5: no more #3, woot :)

Tested in these cases:
8.x-1.0-alpha5 in core 8.0.7-dev
8.x-1.0-alpha5 in core 8.1.1

I'm following this issue: happy to test the permanent fix too.

Seems to work!
Caution: I only tested if this works from the (backend) UI perspective.
(Code perspective testing is not my expertise)

as alpha5 also works, there is no difference seen in UI (errors) with and without the #6 patch.
In both cases the fatal error from #3 is not occurring anymore. (the alpha4 error)

Tested in these cases:
8.x-1.0-alpha5 in core 8.0.7-dev (simplytest.me)
8.x-1.0-alpha5 in core 8.1.1 (local dev)

Patch applied cleanly in both cases, no visible errors seen at Drupal backend UI