Had the same errors. Found the fix.
in /var/www/html/admin/api_FTL.php
change line 308 from
$forward_dest[resolveHostname($tmp[2])] = floatval($tmp[1]);
to
$forward_dest[resolveHostname($tmp[2],true)] = floatval($tmp[1]);
Chart works great now!!
It works if you use true or false…just seems to need a second parameter.
Maybe one of the dev's will see this and add the fix into the branch they are working on.