This problem has been reported before. There is a very long discussion at Possible Bug in Editing Master Sources Some RM users were able to reproduce my symptoms and some were not.
I did in fact submit my database to RM and they could indeed see the problem in my database. However, they reported that there was some sort of unknown corruption in my master source rather than there being a bug in RM. They also reported that doing a drag and drop of my database fixed the problem, as did making a copy of the master source. Well, the original master source was still in use and still had the problem. It was only citations based on the copy of the original master source where the problem was fixed.
I still think there is a bug. Perhaps it would be useful to submit your database to RM for analysis.
In the meantime, here are some questions.
- Which source template are you using for the Master Source with the problem?
- Had you ever used the Customize => Reset To Defaults feature for that particular master source prior to encountering the problem?
- Which version of RM are you using and are you using it on Windows or a Mac?
As it seems to turn out, using the Customize => Reset To Defaults feature is a workaround for the problem. But using the using the Customize => Reset To Defaults feature also seems to cause the problem. By which I mean that after the Customize => Reset To Defaults feature has been used for a master source, that master source will not update ever again without using the using the Customize => Reset To Defaults feature. The thing that was puzzling in my case is that I never use the using the Customize => Reset To Defaults feature, or at least not that I know of.
I therefore wonder if maybe I caused the problem in the first place by using the using the Customize => Reset To Defaults feature without remembering that I had done so. That seems very unlikely, but you never know. For sure, using the Customize => Reset To Defaults feature ought not to cause this problem. Surely that is a bug that could be fixed.