A family of Microsoft relational database management systems designed for ease of use.
Two of my clients have used a NAS for back ends (long before the issue discussed here) and both were troublesome, so I would not personally go down that route except as last resort (but I assume it is a guaranteed solution to this issue). If necessary I would try Mark's method or stick the back end on a spare Windows PC and disable leasing on that. I have no idea how the performance on a fast dedicated PC would compare to that of a decent NAS though, in this context. Your issue seems to be with performance, so I suspect you will have to test the various options.