Trouble shooting

I recomment to use xscanimage for debugging. Used debug levels for SANE_DEBUG_EPSON are 1-8.
export SANE_DEBUG_EPSON=5
xscanimage

Write the messages to a file:

xscanimage > /tmp/sane-debug.log 2>&1

Advanced trouble shooting

There is now an environment variable to force a different command level. DON'T TRY THAT IF YOU DO NOT EXACTLY KNOW WHAT YOU ARE DOING
export SANE_EPSON_CMD_LVL=B5

Use the debugger:

If you are not already root
xhost +
su
export DISPLAY=:0.0
now start the debugger
xxgdb
file /usr/local/bin/xscanimage
run
after crash
stack
that's the output I need.