Did you give a straight answer to this - "And if you believe the police would find JT's evidence credible perhaps you can explain why super-sleuth Amaral dismissed her as a not credible witness?"
No.
I rest my case.
Your theory that Gerry had to relocate himself on the off chance some random person on a balcony saw him, despite the fact that he knew there were two people who would give statements that he was standing in a (slightly) different position is a non-starter. Try and come up with another, more plausible reason. Here's one - all three are remembering the event ever so slightly differently from each other as they are 3 independent people who experienced the event from slightly different perspectives - or is that just completely impossible?
I think I explained that but just for for you........Tanner's account of the positions of Jez and Gerry was given credibility because Jez verified it. How many more ways can I say it?
As to your second question. Gerry positioned himself precisely where Jez and Tanner said in the collective timeline handed into the PJ on the 10th of May :
'2115: JT leaves table, and sees GM talking with fellow resident ("Jez" Wilkins) outside the patio gate of 5A. The two were standing just up the hill from the gate towards Rua A. da Silva Road. She did not speak to GM as she passed.'
Remember this timeline was constructed with both Kate and Gerry's input.
It really doesn't matter why he changed his position only that he did despite him knowing that Tanner and Jez would give a different account