Of course my E3 also does not mined ETC. But, when I still mined GPU 380 2GB so 2 (??) years ago, so after a change in the epoch when the 2GB GPU was not enough. But it was enough to swap only one for 4GB in the rig, the others was just 2GB, and the whole rig was mined at full power for ETC. Unfortunately, it is probably not possible to do some trick in E3....

And I think that even though there is 4GB of memory per module in E3, maybe it uses a bit of memory outside and that's why the problem is now when the DAG ETC is 3,57GB. This is similar to having a 4GB Flashdisk and using only 95% max.