If the TiVo is rebooting, that's a fault and should be reported. Unfortunately, you can only expect a like-for-like replacement.
If your friend has VM broadband, they meet the requirement for a V6 and would undoubtedly benefit from changing. The most reliable method is to follow the package re-grade route - I.e. to re-sign onto a current bundle deal in exchange for a new 18month contract and box-swap.
You can ask for a swap if you report the TiVo faulty, but it would be at VM's discretion and only a like-for-like swap can be expected - it's not the quickest box but does remain fully supported.
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