MPSTART resets MPSET values

On one system:

MPSET 0,1
MPSTART 2,"Test"
PRINT MPGET(MPLOCAL,0)

On the other:

MPSTART 2,"Test"
PRINT MPGET(1-MPLOCAL,0)

Both will print 0.

I don't think this is a bug. It's the same idea as SPSET resetting sprite variables to zero, it's just undocumented.

I think the documentation for MPSET is clear on that point:

Gets user-defined data from a specified terminal in a wireless communication session

If the session isn't started before using MPSET, undefined behavior should be expected. In this case, initializing the state of every system at the start of a MP session is reasonable.