Did you try disabling it and see if it resolves your issue? I doubt that is the only difference but a good place to start. My vb4 is a pretty stock install.
Basically it is going to be trial and error resolving that issue.
Did you disable the vb
plugin system as well?
Basically sad to say but its going to be trial and error.
You can also setup a test clean vb
site integrated with classifieds and see if you can replicate the issue. This has to be related to something installed in your site.
If the issue is related to only active when mobile is enabled then especially anything you have installed in vb
that is mobile related turn that off which is why I have stated to try with the vb
plugin system off.
One more thing I noted which I did not see any response to either is make sure you try enabling the mobile viewing in classifieds admin so your not loading vb
headers and footers but doing the mobile how we design it does your application work correctly?