45 brake light issue

Just replaced the brake light bulb on my 45 TD Impression and they all stopped working (2 in cluster, one in tailgate).

Assumed it was a fuse but found to be fine.

Checks the bulbs, all ok.

Tried with ignition on just in case (should work without), still no joy.

Started the car up and they worked!

So my question is why?

If it's something loose, earth perhaps, then it could happen anytime which obviously I'm not keen on.

Was starting the car irrelevant to the fix or did it reset something?

Cheers.

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