It does look dirty, but the pins could also be damaged or worn. So, yes, being dirty could be the problem.
I would try to clean each contact with a high % Isopropyl alcohol (99-91%) and a soft toothbrush, or toothpick wrapped in a bit of paper towel. Be careful not to rub the contacts with the actual toothpick surface.
If all that doesn't work you might need a deoxider made for gold plated contacts, such as DeoxIT® Gold G-Series sold with a micro brush applicator (***G100L-16BX).***
Apparently opening the cartridge is not recommended because supposedly it does not snap back together, and glue might be needed. I have not verified this.