Full beam kills other lights

Posting for a friend who has no internet..
1984 Campaign

After bringing his car so i could  use it as a reference for mine,he went home that evening but found when he put his full beam on it killed the other lights…any ideas please,they were fine at MOT 2 weeks ago,hasnt been out in the rain or driven it except coming to mine..

We did have the rear seats folded and boot carpet up but no other area touched

Thanks, Tim

bad earth ?

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