instead of related data I see weird "___objectref"

my appid is DECCC828-2720-F3EA-FFAD-586EEF9BD600
I’m running BL custom event that have somewhat complex query (several related fields). It worked fine when returned small number of items, but recently I noted that when result have slightly more data (10 items), then it lost few related fields. Instead of real data I see returned “inventory”: {"___objectref": 6}.

__objectref is used to reference an object that has been serialized somewhere in the returned hierarchy. This allows us to serialize circular references and keep the payloads smaller.