@PeteKnight yes, apologies I did not read your post about the WiFi mode and you are correct. I only pointed it out because I had the same issue when using just the ESP8622 chip, I never had this issue when using NodeMCU’s. I still have one powered up that shows up, not just my wifi list but all the apartments around me, I know people think its a free unsecured wifi and try to connect, however it doesn’t seem to cause a problem with connection as the unit has run okay for several weeks.
You are also correct about the ESP8266 being fussy, especially with the power supply. @Madhukesh I no longer use the AMS1117 3.3V regulator, in theory it should be sufficient but in practice it’s not “man” enough for the job during WiFi operations and could be causing your connection dropout problem. As you can see from my sketch all my pullup and pulldown resistors are 10k which if I remember correctly is what Espressif recommend in their data sheet. With regards to capacitors, I have both “storage” and “smoothing” capacitors fitted just about everywhere.
I moved over to the ESP32 about 6 weeks ago and it is much less fussy and requires much less peripheral components. Having the WiFi management on a separate core really helps when you have 4 sensors, an RF link, a touch screen display and Blynk to manage. I still have a few heartbeat timeout issues during peek internet usage times here in China but my main 3 projects (2 x ESP32 and 1 x ESP8266) are able to maintain a good reliable connection now.
The versions I’m using at the moment are:-
Blynk library 6.1
ESP866 core 2.5.2
Arduino IDE 1.8.9
Blynk Cloud server
My advice would be to check or change your power supply.