There is one clue you could try to use: in the 7.2.2's pyMergeDefaults a comment has been provided: "BUG-238945 : Set the original inskey and create properties for the rule to be saved".
If you search for the "BUG-238945", you'd see that there is only one more rule involved - an activity pyMergeInstance. It's also Available, so you could try to align changes in that rule with your pega version.
It turns out that fixes for BUG-238945 is distributed in many other rules too which is not easily detectable even using the Rule Content search. e.g. pzDeleteRuleInDestination where there is a fix in the JAVA step of the 3rd line.
There is no way to confidently say what the total set of rules which actually resolves this issue, since even content search is not working.
In 7.2.2 for the ruleset Pega-RuleRefactoring there are version 07-10-21 to 07-10-28 which is extra on top of 7.1.9 containing 122 rules. Comments with same BUG Id were found in 07-10-25 and 07-10-27 (could be others, hard to detect).
I have raise an SR now. There is no confident way of knowing how many rules and code pieces we need to customize to fix this defect in 7.1.9