If you live in "El Campo" and have purchased a vehicle in Spain, does the address on you registration documents agree with your postal address.  The address is copied from your Padron and used by the seller to register the vehicle.  If this is not your postal address and you incur a fine, it will be sent to the address on the Padron (which probably doesn't exist) and you will then be fined further amounts because you didn't respond (as you couldn't as you didn't receive the summons).  This probably also affect your BASE invoices.

Beware also the post office",will attempt to deliver"then take it
Back to post office .they only hold recorded letters for approx
One week.
The post office send it back to transit,and the cycle starts again.
And the fine goes up each time
Eventually base get involved and they claim the money out of your bank
Traced by your n.i.e number.or put an embargo on the account.
Check the post office on a regular basis.

This applies if the letter ever actually arrives at the post office.  If the address is not a postal address but a Cadastral address then it cannot be delivered.
My adjuntament tell me they are not permitted to use an AP address on your Padron and my Gestor tells me that DGT will not accept one.  Therefor, one is stuffed.
Regarding BASE I made repeated visits to the offices in Amposta and Tortosa over a period of five years or more informing them of my postal address each time.  They finally got it right last year but this year I've had to request the bills by email.
Although I love Spain, the admin is a total joke.