Good point JurajA. I had not thought of that but it would explain the behaviour from minutes to days of working.
I think I need to focus on a newer version than v0.9.5.2_ AT_Firmware.bin since it has this power cycle problem.
I have watched numerous videos and when I flash with a newer release none of them work for me. That is they do not respond to an "AT" command. And I do have pin 4 (CH_PD) tied to 3.3V).
All 7 ESP-01's I have are 8Mb of flash and all firmware versions I have tried (for example ESP8266-IDF-AT_V188.8.131.52.bin) are below 500KB so they should fit.
For example, I followed this link https://www.allaboutcircuits.com/projec ... asier-now/ and it flashes correctly but no response to an "AT" command (while v0.9.5.2_ AT_Firmware.bin does respond).