Product configurator Error - "Variable Non-Existent T_xxxx message"

Since 2021R4 I haven't been able to use the  product configurator as it throws a "Variable Non-Existent T_xxxx message" as soon as there is a (S_xxxx) variable tested in the options/variants or scenario. In my tests, I am not using T_XXXX, just S_XXXX. Even the SEED "Bike" examples are no longer working.

Has anyone found a solution?