There are differences between Pro and Go, Go is more limited in features. I haven't experienced that issue with my portals, but like in your prior post it can be one items that causes a problem. Filemaker Pro came out in 1980 and Go in 2010 ( http://en.wikipedia.org/wiki/FileMaker ), so Pro is a more solid program, also you have to consider that an iPad is in no comparison to a computer in speed. These are aspects that you have to take into consideration when designing a database for Go, iPads being slower is usually expected from most user. This is another reason you may have to reconsider your layout design for the iPad.
If speed is a real issue, you may consider a Windows 8 tablet. (I'm not putting down an iPad, I have one) Filemaker Pro will run on a Windows 8 Tablet PC, which may fix your issue. You will have the additional purchase price of Pro over Go being free.
Note : I know it will run on Windows 8 tablet but I don't know about Windows 8 RT tablet, you would have to contact Filemaker
Thanks for your comments. The Windows tablet idea is one I have not thought about yet. This might be of interest in the future.
Actually, conditional formatting inside the portal does work. It is conditional formatting outside of the portal based on an ExecuteSQL function gathering information on the records in the portal that does not work without refreshing the window.
It nice to know that you discovered the problem, thanks for posting, incase someone else has the same problem.