Aloha,
Got my Bambu A1 after black friday and immediately starting printing stuff and loving this machine. And then a few weeks ago I was printing with some Overture PLA and stepped away. Came back and found a giant glob of filament stuck to the nozzle and covering the hot end assembly and nozzle. After trying to clean it off, realized i needed a new hot end/nozzle and hot end assembly.
Ordered new hot end assembly from Bambu for my A1 and carefully followed online instructions to replace it. Still waiting on new hot end and nozzle. I recalibrated the machine and even reset it to factory settings. Now when I try to print, the nozzle is gouging the build plate and the filament won’t adhere to the plate.
Not sure about the nozzle gouging issue, but the reason for the filament not sticking do the build plate is due to a dirty build plate. This is caused by oils from your hands getting on the build plate. To fix this wash the build plate with dish soap and rinse it off with water 
I flipped the plate over and tried using the side that I hadnt used yet. The filament isnt adhering because the nozzle is scraping it off as it tries to print.
Does bed leveling run normal?
Always good to do the full hardware calibration after hardware changes…
The nozzle should not scrape as the homing makes sure the z position is fixed to the nozzle.
So something must be off somewhere.