Just got a response from Mooch, thankful he responded and @anon96069639, check your PM :
Hello,
I recently finished testing two of those chargers, V3.1, for my patrons and they did not overheat when charging. Certain components reached 130°C when discharging though and the circuit board material under and nearby was too damn hot for its max temp rating. But if the unit was charging then that’s not an issue.
Some questions… - Were the batteries being charged or were they being tested when they blew?
How long had they been in the charger?
Have the batteries ever run hot before when being charged?
Were the battery wraps in PERFECT condition or could they have been beat up a bit?
Were the batteries ever accidentally short-circuited, even for a split-second?
Do you use the batteries until they get hot, chain vaping, and then stop for a bit before vaping again?
Have you ever charged those batteries when they were below 0°C?
Were those batteries ever brought down to below 2.5V?
Samsung batteries spray out through three slots under the top contact when in thermal runaway. The ejecta leaves the battery perpendicular to the long axis of the battery (“sideways”) at several hundred degrees-C. This hot material can easily bring adjacent batteries also into thermal runaway. It’s how the failure of one cell can spread throughout an entire battery pack, destroying every cell in it.
The top contact can eventually melt though, allowing the ejecta to spray “up” and out of the battery too.
Sometimes the shifting contents of a battery can clog the top venting holes, resulting in increased internal pressure. This can literally stretch the battery and undo the top crimp that holds everything inside. The battery then undergoes what is often called “rapid disassembly”. We call it exploding. 
Depending on the location of the fault in the battery it can also burst through the side of the metal can. This can very easily send the adjacent battery into thermal runaway too.
The internal resistance of a battery doesn’t go up much as the battery ages unless it has been badly damaged from severe abuse during charging or discharging. This means there isn’t much of an increase in the heating of the battery as it’s being charged or used.
Charging a 25R at 1A when new creates 1A * 1A * 25mOhms of internal resistance = 0.025W of heat. Even if the internal resisted tripled it would create less than 1/10th of a watt of heat…insignificant. After a couple hundred cycles the internal resistance often has only increased by about 15%-20% though.
If the cells were becoming more and more damaged internally from something the increase in heat would be VERY noticeable. The external temperature of the battery needs to be way over 100°C before it approaches the point where it might go into thermal runaway and burst. A short-circuit though can cause the internal temp to skyrocket almost instantly.
I often see references to “faulty” batteries. But the most often quoted spec for the internal failure rate of batteries from the major manufacturers is one in one million batteries. So, while it’s not impossible that a Samsung battery was faulty the odds that it was are astoundingly low.
Recovering that charger is critical, though I realize it will be unpleasant. Remove the four screws from the back and take close up, very well lit, in perfect focus, shots of the circuit board.
Then remove the bunch of screws holding the circuit board down, many screws are hard to see, rotate the board out of the unit, and photo the other side.
Let’s see if we can spot any obvious failure points internally or if we might just be talking about an external-only failure, i.e., one only involving the battery.
The protection circuitry in the Opus, if functioning properly, can only stop the charging if the outside of the cell reaches about 60°C before the inside of the cell goes into thermal runaway. And that’s only after waiting several seconds for that 60°C temp to work it’s way through to the unit’s temp sensor. A short circuit can blow a cell in almost instantly.
Whew…okay, that’s enough to get us started. So sorry to hear about this but I am glad it wasn’t any worse. Hopefully we can find the cause.
Regards, Mooch
They just have a different accent, and terms.