troubleshooting for an electrician is simple, but a big head ache and lots of running around if you were to bring someone to fix this.
First I would go to your outlet that does not work and check its connections for ground, neutral, and hot. Back stab is fine as long as the wire makes contact. Also that no wire is touching anything it is not intended to.
Next I would go to the next closest receptacles and switches to that receptacle you need to fix (wire is pulled to the next closest to use less wire). Check all the grounds, nuetrals, and hot wires and make sure like wires make complete connections to each other. The likely hood of your issue is that the device(recept/switch) ;closer down the line to the panel from which power is coming, has a break in either a ground, neutral or hot.
Furthermore your house is not to code having your bathroom and beds together, since code requires your bathroom receptacles to be a dedicated circuit breaker with some form of gfci protection. the bath lights are ok with the beds.
If your wires are soldered with electrical tape it is time to update your system by wirenutting pre-existing wires with a pigtail/ jumper wire to make the wires longer and replace the devices switches and receptacles. you can buy a 12 pack of receptacles and switches for like 40.
Maybe a receptacle is broken that feeds power to the 27 V devices, i see switches and receptacles that crack and cause all sorts of different issues. If backstabbing was a big issue they would not invent a device that had backstab holes, you just need quality work done when backstabN.
I only use the terminal screws when using 12 gauge wire that does not backstab due to size.
sometimes you can look in the box and see which side the wire is going.
also your one 15 amp afci is under much strain feeding all those rooms usually two rooms with a bath tops.
no wise words except something sarcastic to make you laugh and forget about your problem. You now have a box for a 12-24 volt usb charger.