I have a Tekin RX8 in my Tekno truggy and RX8 Gen2 in my other Tekno vehicles and I haven't had a single issue. I think the problems you are having are outliers, at least hopefully. Maybe the 7th time is the charm.
I also use the Kyosho Zeal on all my ESCs.
If you do switch ESC'sI know from the Tekno threads that people seem to like the Hobbywing product.