If you wanted it to stop leaking, you'd have put a ring upon it.

I think that with the possible exception of certain obscure fetishists, nobody experiences frustration like a home handyman. Today has degenerated into a living nightmare, with the added relish that this torment was entirely self inflicted.
Nobody dragged me from my comfortable chair and reduced me to a groveling filthy wreck in the ruin of my back hallway, the situation worsening with each moment.
No tormenter to curse. Just some sort of plot engineered by Edgar Allen Poe, updated for the 21st century by me, myself, and I.
 
...after some cogitation, I am of the opinion, that the mission critical tool-a Pex ring compressor- is marginally bent, by whatever thousands of an inch that would allow it to appear alright,and yet be entirely nonfunctional, which is something like some people I have had the misfortune to meet, but have always been lucky enough to not have to work with, or depend upon.
Unlike this tool.
Bah.


Edit: I found this table of crimp ring diameters and pulled out my micrometer
PEX Ring Crimped Diameters
Pipe Size :            3/8”          1/2"         3/4"         1”
Min. diameter     0.580”     0.700”     0.945”     1.175”
Max. diameter     0.595”     0.715”     0.960”     1.190”

Crimper was coming in at .7223" rather than .715", which I probably would have spotted earlier if the damned Go/No Go gauge hadn't gone AWOL. Padded the crimper with ~8 thou of paper and re-crimped.
Leak is gone. Now to re-engineer the crimper, I guess.

Also thinking about it, the last time I used the crimper I was doing some decidedly non-standard crimping,and I believe this is the predictable result.