Can someone explain to me why several pilot have different problems after doing an update?

yep....  too many varibles to get a clear picture in my opinion.

is was my take

Hi. I give you my experience, I told my friend InspektorGadget, the fear or repair that I had when reading the problems I had after updating, also adding the problems that could be read from more pilots. Today I have finally been able to go for a walk with my bird, with the latest update and with fear but with much courage and prudence. I can tell you that I AM SUPER HAPPY, in addition to flying smoothly and super well, it has collected 18 satellites when before it only took 12 or 14, it works perfectly without making strangers. Really happy.

Many are updating separately the drone, the RC, the battery and the app: I think this can be misleading and ease some errors. If you just update by means of the Fly app (you switch on the RC, you connect to the drone and you push on 'updating FW') you update the first 3 in a single step. Afterwards you download from dji website the 1.04 app, you install it and you're done. It works

this could actually be a cause

I think the easiest error to make is failure to get all of your batteries updated to the matching firmware.  If you have the app set to automatically display the video from the drone when starting up, you never see the prompt to update the battery.  so only the battery that happened to be in the drone when doing its update receives the update.

This happened to me, and when I then flew with the two remaining batteries, the drone did a very strange and dangerous thing.  It flew properly until the battery reached 50% charge.  Then it suddenly lost power and dropped to approximately 1 foot above the floor.  It could then not fly any higher than that.

No amount of up-stick could get it to rise above 1 foot.  I suspect it could only maintain that height due to ground effect.

I was testing indoors.  Had this happened outdoors, at any distance away from me, and at any high altitude, it would have crashed and been lost.