I had similar issue and it was one of my buffers not working right. The left buffer worked well, but the right will not let filament pass through. It was stressing and scraping the filament. Still waiting on a replacement from Bambu, their support is majorly backed up.
I got this error twice yesterday while calibrating some PETG-hf. Turns out if you try and set the flow ratio too high and don’t adjust the temp higher, the extruder can’t push the filament through the nozzle fast enough 
. Whoops. I was trying to take a shortcut by just doing the fine calibration based on a flow ratio of 1.029.
Did a cold pull and then decided to just calibrate the flow ratio manually.