The TB with the two switches is an early 1.9.

The TB where you're showing light around the butterfly valve is faulty. You
either need a new one or you need to fix that one. You can fix it by using
JB weld to make a tighter seal: put a lubricant on the brass plate so it
won't stick, then build up JB weld on the TB itself, working the valve back
and forth to get the proper height and to make sure it doesn't stick.
There's a write-up on the Samba somewhere. It's not hard to do.  However, if
there's excessive clearance around the shaft itself, I don't know what you'd
do.