This glitch us "Under certain conditions, skillchains will be resisted". This glitch has, in fact, existed for several years. As to what these conditions are, they change from time to time and it is not an easily reproducible glitch, so I cannot explain simply.
Currently we are investigating whether this glitch only happened to resurface because of the recent patch.
We have considered fixing the glitch, but originally it was planned that in the June update we would redo how skillchain resistance was calculated, so the glitch was left unfixed this patch.