Interesting puzzle.
Recent book by Albert Lulushi, "Operation Valuable Fiend," can be found on Amazon. Lulushi read Albanian documents and spoke to Albanian witnesses; also seems to have extensive sources in US.
Lulushi argues that Philby had nothing to do with the operation's failure (N. Bethell notwithstanding).
NE Albania was indeed the field of play. Lulushi says C-47s (flown by the omnipresent Polish pilots) were used. Book index doesn't mention aircraft losses; does note one C-47 aborting its mission and making emergency landing in Brindisi after being shot up by apparently forewarned antiaircraft gunners.