I found the problem with ent_clone() on the bugs page,
but it doesnt mention ent_cloneskin().

Im getting exactly the same symptoms with 7.66 using
ent_cloneskin(). The same workaround as that listed
for ent_clone() ALSO works-around the ent_cloneskin issue.

Just bringing this to your attention in case it is NOT a
linked issue.