Accepting channel via channel manager fails

Reproduction:

• create project and add one channel (I used Hippo Acceptance Project)
• open the channel by clicking it in the channel TAB of the project
• make a change (I added a banner on the home page)
• submit the changes via channel menu of channel manager
• go back to project and click "start review"
• Refresh the browser (F5) to work around issue ENT-1934
• open the channel again by clicking it in the channel TAB of the project
• click on accept in channel menu of the channel manager

Expect 
channel is accepted and accept/reject are disabled

Actual 

channel is not accepted and and accept/reject are still enabled and a toast is displayed with text "project out of sync, reloading ..."