Saint-hyacinthe, QC
I'm sorry to say but I can definitely spot corrosion damage on the board.
In red , definitely corrosion
In orange, probably corrosion
In yellow , if this is just board work it's definitely dirty work. Maybe pins were reflowed and old flux is still present. The IC doesn't appear to have been changed and it is very dirty so most probably is corroded as well.
Burned connectors are a typical issue and need both ends of the connector changed and re-pinned.
Until you get the board corrosion free, all non-obvious problems should be blamed on the corrosion first.
Edit: There is most likely more corrosion than I can spot on the pictures you provided.
Cleveland, OH
