I have rig and 3 card amd rx 470, 480 and 570 - 87Mh/s stable and Stale Shares for last 1h about 25% why ??
I have another card witch windows 10 clyamore - Stale Hashrate 4%
best regards
There too many reasons why it might be
First at all you need to check everything linked to the network - wired or wireless connection, bad driver, etc