crossjoin on InventoryGenExits not supported in service layer

I'm trying to fetch data according to Projects that are in InventoryGenExits/DocumentLine details but crossjoin is not working on InventoryGenExits. it says { "error": { "code": 200, "message": { "lang": "en-us", "value": "Not supported query object" } } }.

My query is

https://ServerName:50000/b1s/v1/$crossjoin(InventoryGenEntries,InventoryGenEntries/DocumentLines)?$expand=InventoryGenEntries($select=DocEntry),InventoryGenEntries/DocumentLines($select=DocEntry)&$filter=InventoryGenEntries/DocEntry eq InventoryGenEntries/DocumentLines/DocEntry

when ever I tried to run this query it gives above error.
cross join is working perfectly on other api's but not in InventoryGenEntries and InventoryGenExits