This one would fit either the Industrial or the Supermarket sections.
Anyway I must be going through one of my "Lucky" periods.

Are you sitting Comfortably!!!
Basically I was working on a Bitzer pack with three screws,changing the oil filters.
This pack suffered a major leak recently.
It was one of those sites where you get the "we have done nothing" Answer!
( now please wash your hands after visiting the toilet. Is in 5 different languages!)
Anyway none of us could find the leak and having been recharged. Has been running OK for several months!

So I am kneeling on top of the pack, between comp1 and 2. Shutting the discharge valve.
When I shift my weight from one knee to the other, (as you do!)
I put out my left hand to balance, touching the liquid line going into the Economiser port on comp1.
The pipework moves, it is loose!!!
Basically what I discovered is whenever comp 1 is running and has reached a evaporating temp below approx -30c.
Its economiser port rotalock was contracted enough to make it loose and leak!
Whenever it warmed or unloaded pipework became rigid and gas-tight.

Like I say another moment of pure luck!
Although Monkey Spanners and others have touched on similar stories.
I felt it was worthy of mentioning as I am sure similar will happen again to someone!
And someone may "benefit from the story.
Cheers Grizzly