Missing CLR namespace in AX environment

Hi guys,

Have you encountered this issue in the standard classes in AX… some CLR namespace is missing and upon compilation and an error appears. kindly see the attached screenshots for the reference.

It appears that some CLR namespace is missing. The classes involved is in standard and no customization involves. I need your help on this one.

Thank you in advance!

Just to add. This occurs after I install a hotfix given by microsoft to fix the inventory re-calculation issue. while performing the software update checklist. this error appears in compiling classes. this error is not appearing in full AX compilation.