1-wire sensors die

I’m having a very strange issue. I have a raspberry pi coupled to a DS2482-800 and then a whole bunch of DS18b20s. Most of the sensors have been running reliably for a year now. But there are four of them, which i have swapped out several times, that just die. I have swapped out the DS2482 once thinking it was broken, but apparently not so. Once they have “died”, i can still use one at a time with an ESP8266, but if i connect two none of them are detected. The sensors that die are on the same bus, but doesn’t seem to matter if i change it. I have been chasing this error for half a year now, and i’m at my wit’s end. Waveforms on the bus seem fine, checked with oscilloscope, and as i said the other sensors have been reliable for a year. Any idea what to check next?

I would check the voltage levels on the VCC pin with an oscilloscope. It might be that one of the capacitors in the power supply has deteriorated causing a too low voltage or, more likely, a too high ripple on the voltage. Or you have now more load rpi and the power supply is too weak, in which case a large power supply could solve this.

Thanks for the suggestion. I don’t believe it’s that. Ripple is about 5-6mV.
My last two sensors died three hours ago. Have ordered more and will try to put them on another bus.