MarionQuilts ... but in her declaration that there is nothing wrong, is she using the same set up as you and making it stitch properly? Unless/Until she does, that is not an acceptable response on her part.
So, you have done it in front of her and had problems.....
Then ...... she should be able to get you to do it "right".
As for someone coming to your home ....
.... that's the support you should be getting from your dealer in her shop.
As for you doing something wrong when FMQing ... of course, it's possible.
Though you are able to FMQ, and quite admirably so! So it's not that you do not know how.
Going with the assumption that it is the fusible web ... are you ever able to get it to stitch properly in any form with the web? If so, then see what is different when it fails. If not, eliminate the web and do some sample work to acceptable levels. Then using the same settings and options, do a sample with the fusible. Make notes as you make changes.
When I am messing around in this way, I keep a Sharpie handy, and note next to every step along the way, what settings, needle, thread, etc. Just be sure to only change one thing at a time, otherwise you don't know what created the success.
It's all a slow and tedious process and if you are like me, you feel like you are "wasting" a lot of good fabric to get to the desired end. I know you are up for the challenge .... and will figure this out.