Hi Richard,
Yes, HJT should (although sometimes not straight away) show up something to point us in the right direction, but a few of the latest ones don't always.. it's a real pig basically..
Even when HJT has a big flag waving at us, going "I'm here, fix me if you can" it can prove extremely difficult to fix in some cases, but then that's half the fun, I sometimes forget what the other half of the fun is though..
Cheers
Liam