Process Model alert send to all admin even it set to specific user

Question

I have process model which run subprocess. Both main and sub process already set alert to specific user. 
 However, when error occur on sub process, alert email was sent to all admin in environment ( admin@xxx.appiancloud.com ) 
 Are there any workaround for this issue? 
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 Following is main and sub process configuration. 
 Main Process

Sub Process

Harsha Sharma · Answer

Hope the process model is published. Check if the user is active. If the user configured in Alert setting is deactivated, all environment admins will be notified. As per best practice have a group of users configured in alert settings instead of a user. User's dont get promoted to higher environments, groups do!

Shubham Aware · Answer

The alert falls back to all admins when the recipient can't be resolved i.e. the user is inactive or the value isn't the exact login username( select them via the picker so the correct username is inserted.)