Ah, in between I found :
"Extra option: nounits As of STACK 4.3, if units are declared in a question then the whole question will use a units context for parsing inputs. For example, in a multi-part question you may use a matrix input. If you do so, and use variable names, then these will be parsed expecting them to be usits. To prevent this in a particular input, use the nounits option"
"Extra option: nounits As of STACK 4.3, if units are declared in a question then the whole question will use a units context for parsing inputs. For example, in a multi-part question you may use a matrix input. If you do so, and use variable names, then these will be parsed expecting them to be usits. To prevent this in a particular input, use the nounits option"