I am experiencing some strange errors and issues working with deliverables in Project Online. I am able to create deliverables, but it seems that after I "sync deliverables" a couple of times, it results in "An internal error occurred" and I am no longer able to save, check-in, or do much of anything with the project. I found and used Allan Rocha's blog, which seems to clear the issue and allow me to continue working with the project - but then, the same issue will happen again. I am thinking it must be something with the stored credentials synchronizing between Microsoft Project and the SharePoint Online site? Has anybody run into this before? Any suggestions for next steps?
After some additional testing, I found that I can click "Sync
deliverables" without any issue, but it is when I bring up the "Manage
Deliverables" pane in Project Professional 2016 (Version 1711 Build
8730.2122) that it causes the internal error.