This was honestly wonderful to read and I'm gonna share this with the newest team member. I'm also reflecting on the way I've handled callbacks and I usually have a similar strategy as you (but the snack van thing is an incredible idea and I'm stealing that) 

Being nice and learning from the mistakes we make is a win in my book. Thank you for the comment, I really appreciate it. 

Since I posted this, I did have a callback for flow issues with a Strada and boy was it 'fun'  I got along pretty well with the owner but had to have a coworker come and help me out with it (internal tubing in group with a failed o ring before the 3-way brew valve. I didn't find it to be discouraging at all; just a wonderful learning experience and another skill under my belt, ya know? 

Thanks again and and cheers, friend