It CAN be a genuine bug. If that's the case, then, another removal request should resolve the problem, but only if the bug have been corrected.
Some other possibilities are :
The other person, not getting his e-mails, keeps on mistakenly signing up with your e-mail address. Your e-mail address is removed, only to be re-entered by that other person. Real possibility as at least 3 other peoples, in 2 countries, keep on entering my Gmail address instead of their own.
They may have a very serious problem with their system that prevent them from effectively removing your address.
They may use a third party mass e-mail service, and that service is poorly maintained, or have some shady dealing with some SPAMMer...