AOZ Studio V1 (TBD bugs clean/-> V2)

My contender for 'Weirdest Bug' award.

This code throws up an internal error:-

S=12345
S2$="000000"
S1$=Str$(S)
SL=Len(S1$)-1
S1$=Right$(S1$,SL)
Right$(S2$,SL)=S1$

If it is changed to this (ie: adding something to the end of line 6, no error:-

S=12345
S2$="000000"
S1$=Str$(S)
SL=Len(S1$)-1
S1$=Right$(S1$,SL)
Right$(S2$,SL)=S1$ //No error now

Or this:

S=12345
S2$="000000"
S1$=Str$(S)
SL=Len(S1$)-1
S1$=Right$(S1$,SL)
Right$(S2$,SL)=S1$ :