Members keep being moved to former members but do not click on link in email

Good Morning
I am the admin for the Kelowna AM Toastmasters club (5300).
For the last few months we've noticed that multiple people have moved from Members to Former Members without clicking on the Not A Member link at the bottom of an email. 
I have to keep reinstating people - moving them from Former Members back to Members. In some cases it has happened to people two or three times now, over a number of weeks.
I've been told by some of those affected, that it is as if the whole email message is the link not just the line at the very bottom. They tell me that they have definitely NOT clicked on the Not A Member link.
Please could you take a look as this is wasting a lot of time plus some members are missing out on emails until we realize what's happened.
Thank you
Moya Webb
Treasurer and Admin, Kelowna AM Toastmasters, Club #5300, District 21, Division J, Area 70