iSupplier account notifications being turned off

Has anyone run into a situation where the notification setting on iSupplier accounts will turn itself off (i.e. to 'disabled' or 'do not send me email')?  Occasionally when we try to reset a supplier's password through the Manage Users screen, they do not receive the email.  When we reset them via sys admin and log into their account, we see that their emails are turned off, which also disables the password reset emails.  The suppliers tell us they never changed that setting.

First, is there any way to have the password reset emails get through even if the account settings turn emails off?  Second, is there any way the system could be disabling their emails without supplier involvement?  We're on 11.5.10.