The same rules, only one being triggered
That is a weird one.

I don't know what caused the problem but the fix was to export and import the rule.

The interesting part is that cloning the rule did not work, even when I simplified/changed the cloned rule to 

{ "rules_tc_admin_review_cloned_" : {
    "LABEL" : "TC: admin review (cloned)",
    "PLUGIN" : "reaction rule",
    "REQUIRES" : [ "rules" ],
    "ON" : [ "node_update" ],
    "DO" : []
  }
}


The rule was never checked.
There seems to be a bug. Possibly in the rule cloning function.