Besides the official line of “data directory on a network drive not supported, blah-blah-blah,” I have seen this arrangement work well. We aren’t running that config here but have had a similar symptom. We suspected roaming Windows profiles and the “cleanup” behavior of Notes roaming – based on first use, not latest use 🙁 but have not yet hit on a definitive solution. Not much of an answer, but gives you a couple more places to look. Good luck and let us know!