Help: Possible Hardware Failure

[Angrboda]

At present I have port forwarding set up but not a static IP address. My nerdy mate who set up the router insisted. Are they absolutely needed? 

It might. SMB and NAT don't play nicely. However, you've likely got a layer of NAT with both static and dynamic IPs, and your old config took that into account.

So I'm thinking the error is likely to be in the LAN or Wifi settings. Be grateful if you can suggest anything else I should look at.

There's a lot of things that could be involved, which is why redoing things from scratch is usually faster if you don't know what you're doing.

I'd need to know a lot more information to make more specific suggestions, and frankly, solving problems like this via forum or chat is a long drawn-out process that I don't intend to engage in.