We have a bespoke management system that was developed in different times by different people, and hence each system acts like the others don't exist. Our current developer (not me) has been with us for around 15 years (he cares too much to leave, but does also have another primary occupation), and has been maintaining this old asp.Net codebase.

I've been slowly trying to plant the seeds of desire for something else, and we might possibly - by the end of the year - begin to use ERPNext to replace at least one of the systems, and then eventually more.