When you say swapped cables, does that include the ADSL cable? I didn't think of that one earlier.
Any new or replacement electrical or electronic kit just before this started? Including TVs, Sky boxes, exercise equipment? (Exercise equipment next door can cause trouble as well).
[joke]It's the garage floor charging gear for your new Tesla car

[/joke]
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection - AAISP Home::1 80/20. Sync 59240/14753kbps @ 600m. -
BQM