Whenever I try to click the check mark for a user on the registration queue, I get a little error popup in the lower left that says "Error write EPIPE".
After that, if I try to approve the user again, it simply says "Error email taken". However, the user seems to actually be created successfully, and I can assign them to groups, etc. The email that would normally be sent to the user that their registration was successful won't be sent, though.
I'm not seeing anything in the server log about this error, unfortunately. Seems like a redis error but the redis logs also show nothing that is helpful (maybe the verbosity level isn't high enough.) If I can provide any other helpful information please let me know.
I'm at commit 0516418 on the master branch (happy to make this a github issue if that's easier.)
In any case, many thanks for these awesome forums. They are really great!
Please note that its not recommended to use the Master branch for production sites.
The devs like github issues 
At least for issues that occur on master.
EDIT: to keep the reference: gh#4193
