Just based on the picture I'd say that the extruder is too cold leading to the 'stuttering' that you see. If I had to guess, I'd say that when the fan kicks on after finishing the raft, the extruder temp is dropping and not being heated back up quickly enough which leads to the 'fade in' look that you're getting. Try up/downgrading the printer firmware to see if it fixes the issue. Also, there is available on the market a modification that would let you monitor the temperature as it's printing.
Let me know if this helped!
I inserted a new hotend , with new thermocouple and resistance , but the result is the same , I'm doing the downgrading , and tomorrow I tell if it worked , Where can I buy the mods to check the temperature ?
I have the exact same issue.
Do you hear a "clicking noise" when this problem occurs?
No no clicks , you must consider that I have 6 machines m200 , and know very well the machines , the problem is only in those 10 seconds after the object is printed very well , but those few seconds spoil the bottom
Did you compared with another model? Maybe with similar geometry.
Did you tried to slice with an older version of Z-Suite?
This happens with the same zcode in more then one of your six printers?
Yes, I tried it with other models , but the result is the same , this problem has always been there , but often disappears on its own , and it appears in other machines , I tried to do the downgrade , but I did not get improvements , I tried other machines on the same file with the same card and the result is good..