No burning on neutral? Unless something very strange is going on, the neutral in the cable should be carrying exactly the same current as the live. So something must be different about the live cable circuit than about the neutral cable circuit.
So back to poster, That is two of us wondering if the problem is not exactly an overloaded circuit or any problem using 2.5, but maybe a fault somewhere with what you have got. Bas reckons that if the ring live is broken somewhere, it would still work but now the remaining live would be carrying all the current by itself. So it could get overloaded, especially if the break is near one end of the ring.
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