True, it’s a 10409 error on the client. I’m currently rolling out an app update which logs the errors. Later I’ll release an update which uses random IDs for a specific document type. Hopefully this will bring the sync error rate down by a lot. As @borrrden mentioned there most likely won’t be a bug fix unless we, the developer community, create a reproducable sync bug.
I only code for Android. Is your stack iOS-only, @hyling? In your linked thread I came across a comment from snej. There he describes rapidly updating a document on both sides and running into issues. I think with such a program one would run into many 10409 errors, too. But proving that it stops updating and not solving the conflict even if the server has a new document revision won’t be easy. Will it be easier to do so manually? I see that you were able to reproduce it but only every 200th time. Since it is likely a threading issue is it somehow possible to store all the lower level logs until one runs into the issue? To be able to reproduce it everytime sounds unlikely.