More results from my fussings.
I found that my dual LPS was getting to hot for the regulator so it was 'protecting' itself, which is probably why the 3+usb was failing to latch.
So I opened up both ends of the case to let it breathe.
Then after it cooled down and stabilized, I again cranked up the voltage feeding the 3+usb to 6.2 volts and then power cycled it.
It failed to latch, until I lowered the voltage to 6.049Vdc when it latched up and has stayed operating properly ever since.
I see this as more details to help figure this all out.
And granted my dual LPS is WAY overkill for use with these low powered 3+'s which in turn means it generates more heat than a more purpose built LPS would.
So if your LPS case runs Very warm, it may be a good idea to add some form of additional cooling to the case, via either convective or forced air methods.
As an example I added a few vents holes to a Headroom BUDA power amp and used convective cooling and as a result the SQ took a small step up as a result.
So to fix the overheating LPS problem, I have 4 choices.
#1 I can drill some holes in the case and use convective air flow cooling.
#2 I can order a lowered output voltage and lowered VA rated transformer with (dual 7Vac instead of the existing 12Vac windings).
#3 Build up another LPS just for these 2 Mutec boxes.
#4 Add a fan to this case.
I opted to order up a Noctua 80mm 3 speed fan to either force feed cool air into or pull the hot air from the case.
Which is the 2nd least expensive option but the one with the most flexibility in terms of dialing in the amount of added cooling.
Which also brings up the possibility that others may also be running their 'home built' LPS units at or near their thermal limits.
And this in turn may be a contributing factor with these signal latching problems.
I am sorry you hear you are having issues with your LPS. Is it this one?
Here is a HDPlex like my unit to compare how they mount the Regulators on the heatsinks.
Could you retrofit 2 x heatsinks and detach the regulators on the LPS board and then mount those on the heatsink with a bolt and heat cement?
If you can source some heatsinks that fit your sides, bolt them to the outside of your sides, and drill oversized square apertures in the sides. Then gain access to the heatsink inner face.
My HDPlex with no devices attached seems to draw almost zero mains power from my P10. Then when I boot up my Mac Mini which is using 12V DC it then shows a mains draw of about 30 watts. So I assume the HDPlex takes what it needs, and then converts the voltage down to 12VDC in my case. If you have 2 Mutecs drawing then they will up the heat in the LPS?
Does any of this make sense? I am not a tech, but hope this helps.