That steam wand is tricky.....
Well, my filing down the notch on the valve stem didn't solve the problem--my toggle still doesn't lock. Fortunately, it didn't make it worse.
Here's what the steam valve assembly looks like:http://www.1st-line.com/store/pc/Wands-Knobs-c603.htm
Haven't opened the Strega to check the steam valve assembly to the boiler....the problem is within the toggle components.
My next move is to switch the steam and water toggles-- just the knobs and the stainless screw the knob is fastened to.
Maybe this screw is worn?
Meanwhile the rubber band sling is working....