Technician reported an aircraft had a repeat discrepancy for a leaking fuel tank access panel. It was discovered that two access panels on each wing had been installed in the wrong locations and mis-indexed.

Narrative

Aircraft XI received a turnover from 1st shift on Aircraft X. The left inboard fuel tank plate was leaking. Access door XXXXX opening. When I removed the interior plate the rubber gasket was stuck to the inside of the wing structure and had a 5 inch strip of cracked and dry sealant that to me was the cause of the leak. I installed a new gasket IAW with the AMM and installed the plate. Leak check was good when fuel was transferred into the center tank. I signed off the job on log page X.I have not replaced many fuel panels. I had confirmed the tank hole for the write up but was unaware that the plate number for the opening should be confirmed to match.(The AMM does not suggest this.) I realized this after the aircraft came back with the same issue. I had indexed the plate on removing it so it would not be reinstalled incorrectly. Unfortunately the wrong plate was installed previously and I did not catch it on the reinstallation. The index point (door key) was deformed previously so the tank seemed to fit with no hesitation. In my limited experience if a plate is installed incorrectly the then the door key will not let you place the plate in the cavity. It appears the plates for XXXXX and XXXXY were switched at a previous installation. (It was found that the other wing had the same for the two innermost tank plates - XXXXZ and XXXXA) I also found that the plates with fuel sticks have a decal in front of the plate as well. Again not referenced to check this in the AMM. I will be suggesting a tech ops training video on fuel tank removal and reinstallation techniques for our various fleet types at The Company. I had looked while performing the job and there is not one referencing this. I will also be following the fuel pressurization procedures to the letter- as opposed to the 'Norm' of simply filling the tank and checking for leaks. I would say the dirty dozen aviation maintenance gotchas on this would be lack of knowledge; lack of resources; pressure and norms. I've learned not to assume any part was put into an aircraft correctly by a previous Technician.