This! It still very much sounds like a hardware problem.
But you keep shooting at the dark.
Unless and until you have an error message or other proper indication what else it might be, asking us to help you with that is wasting people’s ressources here on everybody’s part.
Sorry but that’s a very inefficient approach.
So first and foremost, please reproduce your problem with a different RPi and a 2.5A or better power supply. Exchanging your SD is a good idea, too.
Does the system ‘return’ after you cannot ping it anymore ?
Does the red LED flicker at times ? Do you see ‘undervoltage’ messages in syslog ?
Read up on the background here.