G0 ignores Z Max Speed
So I just got my first Prusa i3 printer so please help a noob out. I'm running standard marlin firmware ( I think?)
I seem to be having problems with my g0 commands ignoring my z max speed. For example when running the command "G0 F5400 X86.400 Y86.400 Z0.300" the motors slip and the printer doesn't move to the correct position. If I replace the g0 with a g1 then it works perfectly?
Any ideas how I can fix this?