This will work no matter what bytesin[0] is.

ThisWorks:

if bytesin[0]= $80 then Weird
Weird: '<--- fall through to here regardless
HSEROUT ["up",str BytesIn\ByteCnt ,13,10]

Change it to something like;

if bytesin[0]= $80 then Weird
Goto SomeWhereElse ' Jump over weird if bytesin[0] not = $80

Weird:
HSEROUT ["up",str BytesIn\ByteCnt ,13,10]