How can I fix "Custom APL has invalid commands?"

If you cannot start a sim and are receiving the "Custom APL has invalid commands. Only "actions" commands are allowed" error, double check the "Custom APL and SimC Options" section of any sim tool and clear out any text you find in there.

Sometimes text can get in there due to an accidental paste or due to some unintended interactions with browser extensions.

This text box only allows specific SimulationCraft options and will not accept many of the options that come from the default /simc input text.