can't connect to my mac when its connected to 2 seperate networks at the same time

my mac (host) is connected to 2 seperate networks ethernet and wi-fi , both have access to the internet through different isp's , although ethernet takes priority over most things including access to the internet i.e. logmein

when i disconnect either one i can remote in but with both connected  i cant?

i have been remote conecting for several yrs with both connected with no issues

i also have a pc at the same location on the same exact setup which i have no issues connecting to when connected to both networks

so it can't be either router.

does anybody else have this setup on a mac?

have you ever encountered this issue?

for now my work around is to leave wi-fi off and turn it on when i remote in but if i forget i can't access please help