it's pretty strange then  cause if you use variable in L1 you have exactly the same thing than with  a normal var (it's just a memory location in all case). Can I see some problematic code please ?

With one byte values in memory you have to use signed{} to convert 8 bit and 16 bit signed numbers.

For your "variables in L1", just store them in two bytes instead of one (using r) and you'll get the exact same results than with "regular variables" and with custom variables.