not sure if any is having problems with iOS 12 on iPad when you open global maps no aircraft are seen even when you clear data.
Are you referring to the iOS OpenADSB app? If so, it's working excellently on my iPhone running v12.0.1. Actually, I'd strongly recommend this software.
Interesting. If I venture to guess that's Apple slowing your iPad CPU down and it taking a long time for browser to process.