>Andrey, "gluchoje" in Russian must be also an endorheic lake, i.e. there is no natural outflow (Глухое озеро, в которое вливаются притоки, а истоков нет.), isn't it?
Yes, sure.
>There is a "Gluchoje" lake not far from Ekaterinburg too.
Sure, that was not the case. Urals is too far!
Personally I think that it could be near Plyussa, on the way back to Pskov-Dno airfields. As far as AFAIR III./KG 3 switched from actions on Novgorod direction (in support of 39 PzK) to Leningrad area in the end of August.
But as far as "Glichoye" is too common, we can't be sure without any additional info.
Look at:
http://mapo35.narod.ru/map2/index12.html
There are ANOTHER two Gluchoye lakes on the same map there (see quadrant 28/68 for one of them for ex).