We have identified an issue on mac, where the drop down list of scales is missing the Current Scale value. This means that when you select a scale that would come after it in the list (e.g. if your current scale is 1:71.9069 and you select 1:96), the actual scale that is attempted to be set is wrong. This should be fixed in the next LayOut release.
In the mean time, a work around is to select a scale earlier in the list, then select your desired scale.
Sorry for the inconvenience,
Adam