Since the serializer update there seems to be an error in the serialization of an array of stock models via the function $client->products()->updateStockMultiple().
I was able to dig down that, while executing there are only empty models transferred to billbee.

I am not as known to the serializer to fix this issue. Maybe someone can step in?
I am happy to help! :)
Since the serializer update there seems to be an error in the serialization of an array of stock models via the function
$client->products()->updateStockMultiple().I was able to dig down that, while executing there are only empty models transferred to billbee.

I am not as known to the serializer to fix this issue. Maybe someone can step in?
I am happy to help! :)