|Welcome to this forum! It's always refreshing to see someone else involved in this crazy stuff.
I'm sorry to hear of your fall and wish you a speedy recovery. Hopefully no serious damage has been done to your knee! The knee is a delicate part of our body ...
Did you have pivot bushings on your pivot? If not, I could imagine that your plate has worn out and that this has been the cause ofg the failure.
Regarding Seismic trucks I have to admit that I have no experience but am impressed with the technology. I am not sure, however, if it offers a significant advantage to more conventional trucks. But whatever flows your boat ...
: Also, has anyone actually tried cutting lightly used skateboards to use as a base skate plate?
Holger Sander did exactly this. Some people use skis.