I put these items in the auto-processing chests in my shed overnight (with kegs either side), and they're gone. No melon juice, zero items left.
I've tried restarting my game and they're just gone.
My kegs were all in the middle of processing strawberries before I removed the remaining strawberries and replaced with just the melon.
Wonder if this is contributing to the bug?
They finished producing the strawberries that were already in, and all that was in my chest was strawberry juice the next day. Machines were done processing (so they hadn't taken any melons at all, and the melons are now lost)