Could be either, and tbh if you're still using a V+HD box you may find it happening more frequently.
Although if the box is that old, and you're out of contract, you may find yourself better off giving the Retentions team a ring and negotiating a new contract with a box which isn't nearly a decade old.
Either give them a ring on 150 [VM phone] / 0345 454 1111 [non-VM phone] (from 08:00 until midnight, every day), or use the Contact Us link at the bottom of this page to initiate a live chat (from 08:00 until 20:00, Monday to Saturday).
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