Have you ruled out other types of fumes? Eg fresh paint, perfume, scented oil diffusers etc.

Sorry, trying to follow here. Three locations: front door, kitchen and living room. 4 detectors: original front door, new front door, kitchen and living room?

Original front door went off in situ and in the living room while holding it?

New front door went off at front door. Swapped NFD with living room - NFD went off in living room.

Moved NFD to kitchen and it went off in there too?

Where are the K and LV detectors now? Have any of those gone off anywhere in the house? Are THEY functional? (Sorry if you already said, I’m trying to piece the bits together and mighta missed that)

Handwriting - my god, their handwriting

Handwriting - my god, their handwriting.

How has no one said - Roman Ramen.

They actually just meant it was suitable for use with the Nokia N95 phone.

Damn that was my favourite phone. sigh ‘Twas a simpler time.

Jaime is an adorable floof!

I must know the source of your magic pineapple blanket that elicits these floompfs please?

Colloquially a “blast from the past”

Hanlon’s Razor

What a nutsack!

Hey buddy, I don’t want to alarm you, I had a friend lose their cat very suddenly to a saddle thrombosis - which is a blood clot that can block blood flow to the rear legs and become catastrophic. It can happen suddenly and can cause loss of control of bowels, difficulty in rear legs, panting, expressions of pain from cat - ie meowing or howling. Did your vet mention/ rule this out when you saw them?

There’s a link below which explains it fairly well in layman terms. I hope it’s unlikely, it is very serious and early intervention is important and gives the best chance to your little guy. I’d feel bad having seen what my friend went through and not sharing the possibility with you.

https://www.thesprucepets.com/saddle-thrombus-in-cats-5199512