What's wrong with dag 281 epoch? It works fine in my tests. If you to get some support, it's a good idea to post your config.txt file and some hardware info (or log file).
I have a miner hang at epoch 280 (both Rx 470 4gb and Rx 480 4gb). After switch to ETH (epoch 272 it still working well). It is not a config problem it is problem with miner. Check phoenix miner topic and there is same epoch problem with older miner versions
C&p
"Read this if you can't mine ETH or ETC with PhoenixMiner: important message for everyone that is running older versions of PhoenixMiner (before 4.2).
IMPORTANT! The versions of PhoenixMiner before 4.2 only support DAG epoch up to 265. Both ETC and ETH has reached epoch 266 already. To ensure uninterrupted operation, please upgrade to 4.2. If you are mining other coins, you can safely disregard this message.
The reason for this limitation is that we need to perform some quite complex calculations for each future DAG epoch in order to increase the hashrate of the optimized kernels. Recently we have added more computational resources and PhoenixMiner 4.2 will work without problems up to DAG epoch 329. We will increase this number significantly (e.g. 400 or more) in the next version."
Phoenix miner works another way than Claymore's. It use optimized kernels wich is must be calculated with depends of DAG epoch. This is why if miner didn't contains optimized kernels for some DAG it would give error.
Claymore's miner didn't use kernels optimized for each epoch. So it must work on any DAG. You must provide your config, bat file and log to determine what's your problem.