2017 sentra question

HI, i have a question. 2 times now my cars power seems to go out. for example, i turned my alarm on in the morning at work then when i leave afterwards, my key fob would not work and the thumb button on the front drivers door handle would not work either. however, when roadside assistance came out and opened my car the engine starts normally, but everything electrical had reset (clock ect). this was about 2 weeks ago and it happened again today. luckily i didn't lock my door, but i tried to use the fob to open it thinking it was locked. nothing happened. i changes the fob battery about month and 1/2 ago and the car battery last month. any advice? another question, can i get a backup key for the door? the one in the back of the fob doesn't work for the door. i hope this makes sense, I'm a layman when it comes to cars :)