That something is a ZMU (Zone Management Unit), they are downstairs in the equipment bay under the floor behind the flight deck (you walk over the hatch as you come in 1L). They can often be reset with a circuit breaker but with regards to your point about flight safety, we wouldn’t ask crew to go down there unless it was for something absolutely safety critical. The comfort of passengers unfortunately isn’t worth the risk.

This is a very common occurrence on the 777, especially the -200’s. Many times I’ve been called out to it at LHR.

Actually in aviation we much prefer speed tape. It’s a metallic tape you can use on the exterior but also does a great job on seats, overhead lockers, parts of toilets and carpets etc...

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Whilst I appreciate you said you’d ask first, I’d caution against anyone reading this fixing things themselves including cabin crew. This should be left to a licensed aircraft engineer otherwise we’re opening a whole Pandora’s box of problems!