I am with a driver version: 19.4.3 and Phoenix Miner 5.0e Windows/msvc - Release build. When the miner makes a DAG for epoch #340 is ok. But the 4GB card stops when the miner starts to make a DAG for epoch #351.
Do you see "Unknown OpenCL driver version! Hashrate and stale shares may suffer" in the beginning of your log?