Yeah, this is pretty common. Its why the Kisado converter was developed. The fix depends on what converter you have. I believe one of them has an actual design defect; a misrouted tracing, or something...I might be just thinking I remember something that isn't the case, if so, sorry.
Usually its just some games that mess up, not all of them. Mad Stalker doesn't run for shit on one of the converters, and I think it was the "Super TV Game Converter" that causes Sapphire to crash on stage two.
Also, I think it was theorized that Arcade Cards are slightly thinner than most HuCards, and that might cause problems with the connection.
My personal theory is that most of the converters are just cheesy aftermarket crap from HK that didn't work very well when new, and are really screwing up en masse now that they are 15+ years old.
As has been said here a million times before (at least 324,000 times by myself): converters are pointless and stupid. The reliable ones cost more than an entire PC Engine Duo RX, and the (comparatively) cheap ones don't work for crap, so just buy a PC Engine and save yourself some cash (and dignity, I mean it so ghetto to have those things sticking a mile out of your system).