I just got my A1 and am having this issue 1 week in. Has bambulab pushed a fix yet? Are others still experiencing, should I just make a habit of lowering my Z before I send a print right now?
It’s normal, it’s just a safety mechanism.
Imagine if for whatever reason your nozzle was touching the build plate, and then the print head moves, your plate would be scratched and damaged, by lifting the z up, it prevents any possible collisions.
It makes a loud noise when it hits the top of the z as there is no physical switches to detect it’s at the top, so it uses the motor to tell it’s at the top when there is lots of step losses.
I fixed it with a small modification. It’s tested and works with A1.
Change this:
;=====avoid end stop =================
G91
G380 S2 Z40 F1200
G380 S3 Z-15 F1200
G90
;-------------------------------
To this:
;=====avoid end stop =================
G91
M17 Z0.3 ; lower the z-motor current
G380 S3 Z-5 F600 ; avoid hitting top z and noise
G90
;-------------------------
That change removes the 40mm up movement that hits the top crossbar.
Also lowers the motor current and feedrate for safe movements at this point.
I noticed that if I not move a little down the Z-axis, it will hit the top when homing the Z-axis, so to be safe i move the Z-axis just 5mm down.
Normally you will not hit the bed because when a print finishes, the z-axis is moved up more than 5mm.
Avoid moving down the Z-axis manually when the motors are off 
Hope it helps
This is happening to me too, and because I have a top mounted AMS lite the cables at the top of the toolhead hit it when it goes too high with a grinding sound. Manually lowering the toolhead and then restarting the print always fixes the issue, but it’s made me a bit paranoid about starting a print.
I have seen/heard the same issue with my Bambu A1, but its not actually the Z-axis movement.
it is the Extruder Backing out before the filament has been cut,
I have specifically seen it when I have had to cancel a Print and then reprint.
Same here but in a different scenario. I’ve stopped a print in the preparing phase. When initiating a new print. The head struck the upper stops… Scary scary noises and behavior! Only a restart worked to manually tap down on the Z axis. Hope nothing is hurt after this.
The issue is still there after one year ! My A1 hits the top at the beginning of next print… Not good and easy to correct in gcode, very annoying this issue…
I just had this happen, I tried homing the printer after a tall print, that’s crazy, still no fix from bambulab 
is the community gcode still updated and working?