Problem: SSID and Password is not permanent
When i connect via captive portal, at first it stores SSID and Password connects to my wlan. After navigating in modes, ssid and password in json is deleted. So when you power down or reset the esp8266 there is no ssid to connect.
Hmm, I'm really not sure what's the issue here. But one thing I know is the captive portal is not stable at all. This is due to the fact your web client cannot access external content while connected that way.
This may cause some instability, but I cannot be certain. I was actually going to archive this repo as it is outdated quite significantly.
On that note, if you haven't, make sure you are using the exact libraries and ESP core listed as I cannot guarantee how the code will perform using new stuff.