Subscription requests that are forwarded to a Remote Data Adapter should be processed quickly. If this doesn't happen, then the Proxy Adapter applies its own timeout limit (10 seconds) and stops waiting data for the involved item.

Can you find a corresponding call to "Subscribe" for the 'floorupdate' item that is not returning after 10 seconds?

I don't think that upgrading to 3.5 could cause the issue.