Miner didn't support new AMD 20.5.1 driver.
We are testing with the new driver and will release 5.0c soon that will support it. So far it seems that it behaves as the "good" drivers - i.e. allows mining until DAG epoch 373 on 4 GB cards.
Thanks for info! Will waiting update.
If you put 4GB AMD card on PCI-E X 16 slot with 20.5.1 drivers it can even mine after 373 epoch having the hashrate gradually falling (25 MH/S for epoch 380, 22MH/S for epoch 400, 15.7 MH/s for epoch 410, 12 MH/s for epoch 420) as opposed to Claymore who stops at epoch 353 and advises me to go mining another coin.