Hello,
Finally i found the time to search my magazine collection and I found the right one (with a couple other interesting ones I had forgotten and will be reading tonight
): it's in Aéro-Journal n°6 (April-May 1999), where there several articles on D520 use by Italians, French (in 44-45) and Germans.
The latter article has a list of losses between 19 March 1943 and 20 August 1944. There are only two losses in air combat, the ones liste above in Febrary 1944. In both cases the D520 was flying a training flight when it was surprised by marauding Allied fighters.
For losses under Allied losses, the list is the same than what wrote Matti with the following exceptions:
_ the four losses listed by Matti on 27 March 1944 at Chartres were on 28 March 1944 according to the list in Aéro-Journal.
_ these losses include the D 520 1584 according to Matti, the number is 584 in Aero-Journal
On the other hand, another French article in the Magazinz Avions n°88 (July 2000) shows that the 4 D520 of JG 105 were lost under Allied bombs at Chartres on 27 March (with a Bf 109 and an AR 96 of the same school). Chartres was bombed again the next day but only a Fi 156 was destroyed.
So I guess the only thing to correct in Matti's listing is the 1584 serial. By the way the Avions' article has also the WNr as 1584 (probably coming right from German loss lists), but as it had been said above, this serial was never produced.