This is possibleHardware acceleration can be disabled by setting an environment variable. Run it from the terminal like this:
$ WEBKIT_DISABLE_COMPOSITING_MODE=1 epiphany
See https://trac.webkit.org/wiki/EnvironmentVariables for other environment variables that you'll probably never want to use.
If this environment variable fixes your problem, then there's a good chance it's a bug in your hardware or graphics driver, but there's an equally-good chance it's a bug in WebKit. Regardless, your best hope of getting help is to report the issue on https://bugs.webkit.org.