Sorry guys, i kinda worded it a bit wrong.
The engineer blamed the phone.
After he left, it turned out the phone was still plugged back in (hence the high errors) as its plugged in behind a cabinet and not easy to see.
The readings in the OP were after i discovered the phone was plugged in so i removed it took a screenshot and rebooted the router.
I ordered a new phone that arrived yesterday (errors were minimal), and this morning plugged it in and they shot up again.
These are after it was plugged in for less than a minute.
Now, 9 hours later..
Also, My attainable rate has dropped from 58997 to 58642 ( for reference).
Just seems odd that having a phone plugged in, and not being used would cause any errors at all.
I do have one of the [censored] dangly filters so i could try that in the test socket.