I suspect it was only ever using one host name, or at least I think that was the intention. It kinda doesn't make sense with what it's meant to be doing otherwise.
Anyway, I believe it is
this patch that "fixed" the old behaviour which was presumably treating the contents of that field as one single hostname that contained spaces (which of course is not allowed).
Specifying more than one hostname or IP address in the Ping Target field also results in a false "network disconnected" message for me,
unless the DNS Query is enabled and successful. Again, looking at
wanduck.c it appears that this field is only intended to have one hostname or IP address. Having more than one would create a syntactically invalid ping command.
@RMerlin Can you confirm that the "Resolve Hostname" and "Ping Target" fields are only meant to contain a single entry. If so, perhaps they should not accept input that contains spaces. Same for the Dual WAN page.