To be honest, there should be no reason to dump the UMD's in the first place, however, it should work fine because the fat PSP runs a native 1.50 kernel. In recovery mode, make sure that the 1.50 kernel is being used. To access recovery mode, hold the R button while powering the PSP on from a full shutdown. Let us know if it keeps giving problems.
-DarkPacMan77-