Thanks 
Tbh I don't know what the rx path is, but I'm going to a hackerspace tonight and hopefully they do.
But if you have links to learn more about 'rx path', I'd appreciate it.
I did do a search here, but I mostly saw things wrt SQM/CAKE and another one which seems relevant, but I don't understand what it says (and whether it actually is relevant in my case).
EDIT: Router bricked, then not powering up after using self-made serial cable - #8 by anon57995562 seems potentially useful; going to watch the vids.
EDIT2: Not so useful after all