.nds files freezing

Hello, I have recently upgraded from the old Slot 2 SD Supercard to an R4. I love it however I am having some problems with the system freezing mid game. I think it might be related to when it is loading new sections of the game, but I can't help but feel it shouldn't be doing this.
It has no trouble playing music and showing images, I hae also changed the skin without difficulty. I also seem to get some sort of error message when I go into Multimedia (moonshl) but it dissapears before I can read it and doesn't seem to have any effect.

Any help would be greatly appreciated.
I am running R4 v1.18 with moonshell v1.71

That's just how the R4 works. You'll have to live with it. My advice: Get rid of the R4. A SuperCard SD is much better than an R4.