So I was one of the first to get VDSL, I've had it a long time. Over that time, during times of strange and pretty wet weather my DSL Sync goes crazy, resyncing. This doesn't happen every time, maybe 1 in 10 times it rains. Last winter it happened 2-3 times. It happened on Sunday morning.

I am in Mt Roskill in Auckland. 

I have a master filter, installed by Chorus, and recently before an outage my line switched over to Band 988 and I was for about 20 days, getting 70/30Mbps. I had the fault which happened over a period of 3 days, but when I opened a case with my ISP, it took Chorus 8 days to get onsite  and by then the fault had pretty much resolved itself. Regardless the tech despite me asking him not to, changed my port. now I am sitting at around 48/10. 

My belief is that the problem appears to be between my demarc, and the street. I don't think it's too much further from that because I was originally connected to an exchange, and now am connected very close to a cabinet.

Sunday it happened again after it had rained very heavily on Saturday night and seemed to get better as the day went on. The outage lasted about 4 hours. I saw syncs as low as 20/2 and as high as 48/10.

My ISP said they would open a case but didn't have any hope that Chorus would take the matter seriously. 

How do I get Chorus to examine the line between my street and my house for breaks or splits in the waterproofing etc?

Any advice appreciated.