Roland GP-8 issues with sound and effects

[Slash19891]

Hi guys. I've recently bought a Roland GP-8 from its previous owner. He said he hardly ever used it, so the settings are more or less factory. However, I compared some presets with the ones from the manual and many of them differ. Also, there is an issue with the sound - the sound on almost all clean presets cracks a lot. Also, if I try to edit a preset, the changes don't save.
Just in case, it's made in Japan, with American electricity cable, but I'm in Europe, so I use the power unit to turn it into a European one. I also plug it into Carlsbro Stingray 15, not any extra sound system.