Sorted, issue was macro signatures! Checked everything but forgot to look into the event logs,
Event code: CHECKSECURITY
Security check of the expression '(EditedObject.StylesheetDynamicLanguage == "plaincss") || (EditedObject.StylesheetDynamicLanguage == "") || (StylesheetCodePreview.Value == "preview")|(user)administrator|(hash)' didn't pass. The expression was signed by user ''. Remove the signature and re-save the expression by a user with proper permissions.
Going to System > Macros > Signatures and resigning all macros again fixed the problem.