It's very unlikely that `sqlite3VdbeAddOp3` has a bug like this. I can suggest a few things that might help: * first try a variety of experiments with your load on this system but without any of the concurrency going on * simplify your concurrency for test purposes so that it's ultra dumb, just one person totally exclusive * if that works, expand the concurrency options slowly and look to see where things start to go wrong The most likely situation is that on this system you aren't getting the concurrency guarantees that you think you're getting or that you want. That will be hard to diagnose and it could cause bizarre failures that are nearly impossible to figure out. Sanity check the stuff and then add slowly for clues as to where things start going wrong. The likelihood is that whatever is going wrong has very little to do with SQLite per se.