Well, I haven't had 10.9.5, I went from 10.5 (Leopard) to 10.11.6. I far prefer the older systems, but they don't work very well anymore. I've been advised not to upgrade to Sierra, so I won't.

Do the system have anything to do with the problems you have re. vBulletin? I hope you will be able to solve it - best of luck!