I can assure you, the insides are the same - the only thing that changed was the case that it came in. A TV Box Pro wouldn't normally be swapped on contract change - they'd just say to keep the one you have. Not sure why you were forced to swap, but you would still have had the issues you're experiencing with the box you had before.
Given that your TV Box has been swapped already to try and resolve the fault, the issue is more likely to NOT be the box itself. e.g. looking at your broadband connection, I can see data occasionally being lost - sometimes it's just for short periods of time, and sometimes for a few days (e.g. 12th to 15th of April, it was quite bad). If the recordings you're trying to rewind are from internet channels, then this could be the issue.
If the recordings are via your TV aerial, then it could be an issue that has affected your aerial strength since the swap. Maybe snow moved it? Or a building was completed nearby that degraded the signal? Or maybe even just the act of changing the TV box has dislodged the aerial connection a little. It's also been known for power supplies to cause issues - when you received the replacement TV box, did you also use the replacement power supply that came with it?
There are many different factors that could affect this, and they should all be investigated to find what's causing your specific issues.
