I think my neighbour is using a lot of power. We should only be using 10amps max. I have only just sorted my electric lead as it burnt out ( at caravan end, not hookup end ) so I'm a bit paranoid now !!! 😩
Not familiar with your caravan and it's control unit, so a large dose of guesswork.
Possibly 'Reverse polarity' detected. The LIVE and NEUTRAL connections are reversed on the EHU. Also potentially and earth fault. Being as you say your EHU lead has recently been 'sorted', that's a prime suspect to investigate first. See if you can borrow a different one from the site/neighbour to see if that cures the issue.
Possibly a breaker tripped on your control unit and needs resetting.
Your neighbour can only draw up to the supply/breaker limit on the EHU bollard, beyond that he would trip the bollard breaker and be cut off. It should have no impact on your supply unless it's a unconventional set up, say a splitter from a single EHU point.
Sometimes if the EHU network is subjected to a lot of heavy loads, the supply voltage can drop at the bollard, but not aware of voltage sensing being a feature of caravan control units, but I can't rule it out.
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