Install a hyd pressure gage in a tee in the IN port of the splitter valve and you will probably hae your answer.
Somewhere you are blocking the hyd fluid and the engine will probably stall and quit if the relief valve can not handle the volume of fluid.
Maybe the relief is not working
Could be a malfunction QD, or valve lever in wrong position.
If it only does this with the log splitter , it is probably the QD's.