DG, I'm afraid that the problem is that the software for the main website was written on a bespoke basis to meet the commercial requirements of the company at the time. The forum module was essentially a bolt on afterthought at minimum cost which drew on the facilities of the main website to save the need to write a new system. With hindsight it would probably been better to have used free standalone forum software which was developed for the purpose.
The company is unlikely to spend any appreciable sums on developing the forum facility as there is no commercial justification and our main competitor does not offer a forum.
Converting the existing forum data to run on an alternative platform with a different database structure and functions is simply not feasible for cost reasons. Anyway, that way madness lies, although I did once manage to convert a complex MSDOS Foxpro database accounting system (wot I wrote!) to allow the data to be maintained on a corporate SAP system. Even IBM were impressed! The SAP system turned out to be worse than mine though, with less functionality and it only cost £2.2m.
However, as Paul implies, Windows 10 causes compatibility issues with other websites too depending on the browser and hardware used.
Colin