Well for a start I can't see any evidence from the wit stat of Nelson Filipe Pacheco da Costa that he handled the patio doors:
https://www.mccannpjfiles.co.uk/PJ/NELSON-DA-COSTA-1.htm
He refers to entering 5A by the main (wooden) door and searching the apartment. He does not refer to the patio doors and/or searching the back/balcony.
Then we have an anomaly in that according to Germany the unidentified fingerprint originated from a woman or youth and not a male (officer) as PJ claim. Added to which we know for a fact GA was found guilty of falsifying documents in another case.
https://www.telegraph.co.uk/news/uknews/5370361/Madeleine-McCann-police-chief-found-guilty-of-falsifying-evidence.html
Finally my abductor/suspect is female 
Interesting.
In terms of GA being convicted, etc, I would suggest that most police officers past or present will do one or more of the following: mis-handling evidence, not following protocol, intimidating witnesses, overt leniency, nepotism, theft, assault, minor / major corruption, cover up for colleagues, lie for colleagues, failure to follow up for whatever reason, go easy on someone / let someone off, go the extra mile for a local resident, help an elderly person, give 10 quid to a junkie, piss in a suspects sink, lie under oath, embellish an account to get a conviction, procrastinate, make a gut call, not 'call it in', mislay evidence, create or plant evidence, racial profiling, sexual assault / harassment, victimisation or bullying, stab colleagues in the back, misuse of resources, mistakenly obliterate evidence, turn in shit faced, turn in on time for 30 years, etc, etc. They're human beings.