Konic Minolta media feed problem?

My Konica Minolta 3730 works perfectly with plain paper, but when I try to print card, even with all the settings correct, every sheet jams in the feed tray. I can see exactly what the problem is; as the media is fed by the roller it gets as far as the small unpowered "squeeze" roller but that is so tight in rotation (it has a scroll spring on it to make it so) that the feed roller just skids until the machine shuts down with a media jam error message.

If I feed the top sheet of card past the initial resistance point where it meets the squeeze roller, then it will print perfectly - but usually just that one sheet - and will then jam again.

The only though I have had is that there might be some adjustment that opens the gap between the drive roller and the squeeze roller which isn't working - but I certainly can't see any such thing (although, of course, there is no way of checking what's going on as everything is arranged so that any attempt to operate the machine with a cover open will simply give rise to an error message.

I have tried cleaning the drive roller but this makes no difference. I will soon need new toner cartridges and, seeing as though these cost over a hundred quid each, might I do better to simply buy a new printer and throw away my hardly-worn machine simply because it has a very minor fault.