d4rkm4tter: I fixed this, but superko is such a special case that we can add ids where the pruning is turned off. There are other superkos on the website, let me know if you see one so I can add an exception.
posetcay: I think manual override feature for merging could be useful in some cases.
d4rkm4tter: posetcay pointed me at this. This happens, because there is a repeating board position aka superko. The script tries to merge it and breaks because there is too much recursion.
bagelfan: I think that the "(japanese rules)" should be removed. It gives a big hint that there is something special with this problem, since the ruleset is usually not specified.
posetcay: I agree with you, however eternal life is considered to be dead in rulesets with superko rules, that is why it needs to be specified.
Turning on/off merge positions is now in the problem settings. Alternative Response Mode on/off is too.