There is nothing random, if your details match then you are OK. Have you moved address since last contacting DWP / do you use differing names ? etc etc
Under the address at the top right of the letter, what is the ref code ?
It all changed in about June this year. In an attempt to stop fraud all registered voters have been checked against DWP and HMRC records. If you are fiddling somewhere, or haven't updated details, then your details may not...