Only black bottom discs can only be read, burned games/swap trick has a strange problem

I used to be able to use the swap trick with my psx to play most games but after awhile of not using my console it stopped working for burned games. normal black back discs work fine but when in insert a burned disc while doing the swap trick the disc just stops spinning. specifically what happens is the disc pushes forwards just a nudge and does again a second time but then stops after that. please help me out, im trying to soft-mod an old gameshark parallel port cart(uniROM) so i dont need to do the swap trick anymore just as a note i recently replaced my spindle