I've been having this issue frequently. It's resulted in me having to cancel gigs multiple times due to them never registering that I've sent the finished item to the client. It occurs with items made on the Fabricator, the Fizzer, and the Candle Maker station. At first I thought it was because I was sending multiple items off in quick succession, but it's happened even for items that require a single unit of an item.
Had the problem today to when playing on my new save file. My sim got her candles approved, but when she shipped them off and got them approved the box for it did not check off for her.
