TP4056 + switch mode power supply = bad?

[okw]

My kitchen scale (which I love) eats 9V batteries, so I wanted to upgrade it to be rechargeable. I added one of those flat 3.7V li-ion and a TP4055 charger module (https://www.aliexpress.com/item/33039542964.html). Set the boost to 9V (no time to reverse engineer and hook directly into some 3v/5v rail). Everything works good, battery life is awesome. Charging via USB works good (almost hits the spec of 1A). However, when I connected a 6V switch mode PS (http://www.vanson.com.hk/product/smp-27wme/) via the IN+/IN-, I immediately heard crackling sounds, it smelled burned and TP4056 became extremely hot. I disconnected immediately. It's impossible to touch still, after 45 min. Scale powers up, so the boost part of the circuit is undamaged. The power supply shows 6V and has 1.5mV ripple under no load.

Strange thing is, the power supply of a a commercial scale at work went missing, so we bought this particular PS as a replacement. The guy replacing it being a chef (=less technical inclined), was unaware of polarity and just hooked it up. That fried a few components on the PCB pretty badly. I'm not sure if he had it hooked up as + or - center pin. At the time, I just assumed he had it hooked up reversed (since it fried the PCB). I replaced all visibly damaged components and tried it again. It exhibited exactly the same behaviour as my private kitchen scale (though scales and circuits are completely different). At this point, I'm suspecting the power supply is the common culprit.
Could it have something to do with both the power supply and TP4056 being switch mode, and can go into oscillation?

[magic]

Any USB charger is switch mode too and TP4056 actually is not.
It's a simple linear regulator and one potential problem with running it from 6V is that it dissipates over 2W with 1A current.
There is supposed to be some sort of overtemperature protection in it, but something could be wrong with that.

[okw]

Oh, of course Dissipation...
From the TP4056 datasheet it seems I can replace a resistor to lower the charge current (I have no use for 1A). Along with using a 5V supply, that would take care of it. I didn't have USB panel sockets so I need to use a regular plug charger (I mounted a 5.5x2.1mm socket under it).

Thanks! I'll try it and see if it helps.