My Mega Drive's cartridges rarely boot. It's to the point where I sometimes don't want to change the current game because it'll mean 15 minutes of me constantly taking out and re-seating the next cartridge before I finally see a Sega logo.
Once in and seated 'correctly' however, the games play fine. No freeze-ups or weird graphical glitches. It's only the initial insertion where problems arise.
Likewise on my RetroN 5, the games are recognised straight away and are immediately dumped & ready to play. Thus I don't think the problem is with the carts themselves, but with my old Mega Drive's cartridge slot.
I've wiped down the contact points of the cartridges themselves, but is there any cleaning or repair work I can do to the console's cartridge slot itself? Are there any parts that are known to be prone to failure or can be repaired/maintained, or (in extreme cases) replaced entirely?
I'm using an unmodified 'Revision 1' Mega Drive (PAL) if it matters