Thank you for you reply, I've uploaded the worksheet, it can be accessed on the link bellow. The error message is displayed when I reduce the spacestep in the pdsolve procedure for a better accuracy. everything works fine when spacestep is 0.1 or higher. View 7445_Fokker_plank.mw on MapleNet

Thank you for you reply, I've uploaded the worksheet, it can be accessed on the link bellow. The error message is displayed when I reduce the spacestep in the pdsolve procedure for a better accuracy. everything works fine when spacestep is 0.1 or higher. View 7445_Fokker_plank.mw on MapleNet