Do you mean Export Data in the survey123.arcgis.com site? (I can't see an export data option in the REST interface). If there is some other export option that I've missed, I'll be keen to try it.
EDIT:
Oh, hang on, I think you mean the Export Data option on the feature service in AGOL. The reason is that I was ignorant of this option.
Tried it just now, and it works! So thanks. This work around should do the trick for us for now.
I'd still like Survey123 (and create replica) to be fixed, but in the meantime, I now have a work around. Thanks. 🙂
EDIT AGAIN:
No, actually that fails too. The "Exporting" text appears for a while, and then disappears. If I then go to the location where the new fGDB was supposed to be saved it is there, and I can download it (which is why I thought it worked), but the downloaded zip file is only 189 bytes, and cannot be unzipped.