Yes, it's permanent. I would like to know WHY the failure count is increasing, but if it works ...
Your router boots from slot A unless the failure count reaches a certain threshold, then it boots from slot B. In my case, slot B contained non-bootable info, (soft) bricking my device. By resetting it to zero at every boot, it will never boot from slot B and should it boot from slot B for any other reason, it's the same as bootting from slot A.
Wireguard works fine on this device by the way, I use it all the time.