VDSL (and IPv4!) drops (and fritzbox crashes)

I've been having problems since late 2019 with DSL carrier drops and IPv4 losses from my local DSLAM cabinet

Usually this happens in waves - I'll get periods of this happening several times a day for weeks and then weeks of "steady connectivity"

About every other VDSL carrier drop also crashes my Fritzbox (7390 and 7590 units)

Openreach claim the line is clean, but the IPv4 drops are pointing further upstream - when I lose this the DSL is showing as rock steady - but the ISP (Zen) claim there's no problem being logged in their network)

My suspicion is that there's an intermittent fault in the (aging) DSLAM cabinet being triggered by physical activity as a good chunk of the time when this starts occuring a look down the road shows someone's got their head in the cabinet

The interesting part about _that_ is that Openreach are denying to my ISP (Zen) that anyone was working in the cabinet at the times observed...

Has anyone seen this kind of issue and if so, have you had any resolution?

In reply to a post by Stoatwblr:

About every other VDSL carrier drop also crashes my Fritzbox (7390 and 7590 units)

To me that suggests the opposite cause-and-effect: that there is a problem with your Fritzbox which is causing it to drop carrier and/or crash and/or drop IPv4 packets. (Bad firmware? Overheating? Glitch on power line or earth fault? Nearby ham radio operator?)

It's certainly odd if it's happening with two different boxes. However a line drop should *never* cause the router to crash, so if nothing else, there's most definitely a problem at your side when that happens.

Do you have any fancy configuration on the box - e.g. QoS/queueing, VPN or tunnelling, VoIP etc - which might be unusual compared to a regular user, and hence could be triggering the bug?

I'm guessing the FritzBoxes were supplied by Zen, but do you have something else you could try?

Fritzboxes (like Drayteks) get stroppy if DSL conditions change wildly underneath them

The Fritizes are personally owned, but different models (7390 and 7590), using quite different chipsets (7 years apart in age) and firmware. No fancy setups on them

The nearest HF HAM I'm aware of is over 400 metres away from the cabinet and adjacent to another DSLAM. I've tried RF clamps on the incoming line anyway

I would agree, a drop of line should not crash the device. I would suggest the device is poor, and fix that as a starting point. Once it's not crashing, if the issue persists, in terms of drops, it's time for openreach. When I had a fault, I had 30+ drops in a day, with no router crashes. It would just resync (often very slow).