problem

For an unknown reason changed segments are not saved back any more to GroupShare.

GroupShare answers just with:

{"action":"Discard","errorCode":"OK","translationUnitId":"00000000-0000-0000-0000-000000000000","translationHash":"-1512197268"} 

solution

After playing arround, it turned out that the confirmationLevels settings was missing in the update request - which was not needed before:

'confirmationLevels' => [
    'Unspecified',
], 

With that it works again.