John - I think all of us who fire these models can understand your frustration!!!!!
I for one have spent way more on having a stockpile of carts and parts than I have for the actual models themselves!!!!!
I usually video my models when I fire them, and more than once on camera I have caught myself swearing due to a malfunction, or in the worst case- breakage of a part.
I think my worst experience with this was my Tanaka Glock 17. I expected it to run very well out of the box (I think some of them do!) but mine certainly didn't! I broke 2 barrels and cracked a slide before I figured out what I needed to do! Now it runs perfectly, but that was an expensive learning curve!
I guess if I ever get a Marushin M84 that I'll try to remember to get a few trigger bars for spares!