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? If that's the case, perform clean reinstall of your driver.
Not a message like this. Everything looks ok in the beginning, but when it starts to change from epoch to epoch first gpu starts to mine with a lower speed and after a while the miner crash.
P.S. My monitor is on GPU 1...