[UPDATE]
Ok. I flashed back the Sovol last FW [1.1.0] and everything turned ok, The printer auto homes and Y axis moves as it should do.
Tried again to flash 1.15.6 and nothing… No Y axis and no auto home again, so I ended definitely turning back to the Sovol last official FW, almost for the moment.
Yes, the printer works but I keep on waiting some help, because I already miss the features of the updated FW! FWIW, I especially found Tramming and 64 points leveling very interesting and effective in solving manual assisted bed alignment: while printing the two calibration cubes, I had a very good 1st layer as never before with SV04. Unfortunately, I had not the opportunity to explore more… @Bjoern , I hope you could help sooner or later.
Thanks anyway! It was good while it lasted… 
Hi again,
first of all, I would like you to understand that it is just a hobby of mine to improve the SV04 firmware & to answer questions about it.
Concerning your observations:
You did enforce a factory reset by sending M502 to your SV04. That erased all calibration settings including the offset data (which I recommended to write down) & set them to the default settings for my SV04 that came with this firmware version.
The way to solve that is entering your offset data again. Then save (M500) & rerun the leveling process as described in my wiki on GitHub.
That should do the job… if not, try doing that without using the host system - maybe this is the problem source. If the problem still remains without any host system, re-connect a host & post the output of a M503 g-code instruction here.
Good luck!
Björn
Hi Bjoern and thanks a lot for your answer.
Yes, I know and I appreciated so much your work I read about for a couple of days up now, first for letting us all to take advantage of your time, work and experience. I apologise if my post was suggesting differently. That said, I was asking your help just because I immediately realised - as capable as I am - that the firmware update was a terrific improvement and was disappointed to not being able to find by myself a way to clear my stupid forced errors.
I’ll try again, following your tips. Thanks again so much.
Gaetano
I made an account to say this - the SD card has to be 8GB to work easily. It took me forever to find this info, so I wanted to make sure I mentioned it again. And it might be worth mentioning on the Github for any future travelers.
Hello konokaiden & welcome to the forum!
Thanks for letting me know - in the past there were several discussions about SD-card types, sizing & so on. Some users reported successful installation using SD-cards of higher capacity.
Anyhow, I added a note on SD-card capacity & format in my Github Wiki.
/R
Björn
Thanks, and it looks good!
Yeah, on my end the firmware seemed to flash fine on 32GB card (got the .CUR changeover), but the screen absolutely refused until I found an 8GB card to use. Then it worked first try.
I look forward to trying it out. I’ve been using stock firmware since i got it roughly a year ago, but I’m trying to get 0.2mm nozzle working with PETG at higher extrusion speeds, and I need the higher temps your firmware allows for (yes I have all the upgrades).