That is a bad decision and could leave you vulnerable as that folder has in the past been used to plant malware, when doing exclusions you should be as precise/unique as possible. If it only effects one file then you should exclude only that file.
You may have a problem with your entry, what would be helpful is to post the complete text of the exclusion and we can check it.
However, you could copy and paste this C:\WINDOWS\SYSTEM32\DRIVERS\etc\MchinJdrv.sys into the Exclusions lists, especially the Standard Shield, Customize, Advanced, Add list as that is what is detecting it on-access.