dpmiller

built-up heads like that are more common on hydraulics, I think. Can you get piccys of the whole manifold assy- are the 3 valve just bushed together or is it a single base? what's the thread size of the hose fitting?

Yes. IIRC there was a nominal fee attached but this was discounted off the order.

BPC do everything except work out the duct routes...

can't trust the numbers then as the shiny surface is innacurate. Wrap some tape of some kind around the pipe wherever you're pointing the gun...

how are you measuring the pipe temps?

has the flashing behind the vent stack just drooped a bit?

before going down any 3d printing rabbitholes, how tight in the bleedin thing? How about a nice photo for us to help...

so what's it doing/ not doing?

Howdens Hockley comes in gloss white and is 18mm door? https://www.howdens.com/kitchens/fitted-kitchens/hockley-mirror-gloss/hockley-mirror-gloss-white

this is a problem with PoE, damp gets conductive at dc volts... Remake the plug, give the socket contacts a gentle scrub and try to remove some of the (conductive) black crap in behind them, then goop it up with vaseline or silicone grease as per @ProDave

what is the distance to the boundary?

Tapit fasteners used to have a similar threadform, hammered into a plastic wallplug, but removeable by screwdriver. https://www.carpetfittersshoponline.co.uk/tapit-nails-rws020-46-p.asp

most of my dewalt is the old style but I've moved to the newer batteries to go with a couple of new tools. No hassles with the tools but the contacts on the cheap adaptors aren't great and can get a bit toasty and melty if you push things too hard.

on or under the evaporator core

check the door seals carefully, and if they're all good and you're handy with a multimeter see if the defrost heater is burnt out...

who exactly is the "we"- you or a contractor, and who is hiring the crane in?

You'll need to use a cable calculator to confirm- maximum current demand vs length...

Our steel garage came with an insulated aluminium-slat roller door. It's a Garador IIRC which is a subsidiary of Hormann. It's smooth in action, quiet, and reasonably wind-tight.

there's likely a motorised flap to open the path to the fridge; defrost and retry, but I'd be asking why it hasn't auto-defrosted itself. Have the doors been left open at any time?

is that duct attached with masking tape?

^ this.

any chance the motorised head is slightly loose from the valve?

I suspect the off time will have to be extremely short- arcing- if the burner continues to run without a flameout and purge. I'd be more inclined to say loose connection near the TPV, or a *failing* microswitch

what make of burner is on the Grant? Is it blueflame or modulating in any way? / what happens on yours if power is interrupted for a shorter time even, half a sec or less?

have the various pipes been CCTV surveyed? That would be a good start.