While doing a math operation on a dimension within a model, using quotes (double prime, " ) the operation failed. It either stayed unchanged or you cannot click ok. However, when using "in" for inch the operation works. I am able to do this operation using quotes on other stations. I haven't found any solutions or seen anywhere on the web where someone was had the same issue.
Example 1: 408mm + 2" (does not work)
Example 2: 408mm + 2in (works)
Solidworks 2016 SP 5