I bought 2 of these for 1000 extra feet. Works fine for me: https://smile.amazon.com/gp/product/B000GB0CQK/

This works for me: https://smile.amazon.com/gp/product/B000GB0CQK/

I've bought two and used all of the first and half of the second. Works perfectly for me. I connected it to the original wire using cheap waterproof wire nuts.

If the light is green on the base then it is a solid connection throughout.

I have around 1500ft (420m) long for my perimeter using this 18ga wire mixed with the original: https://smile.amazon.com/gp/product/B000GB0CQK/

Regarding your wire missing error, I've only encountered that in 2 types of situations. First one is my mower accidentally digging up and cutting the wire. Second time I had laid a loop (to exclude a tree) backwards crossing itself.

Honestly I'd say just go for it. If your time is valuable and worth more than what you save for getting the non branded wire, then get theirs. It's just copper wire with an outdoor coating, nothing special about it.