I would recommend you look into it more. Besides the known 7-8-7 shift issue, anything else is abnormal and should be fixed, especially if still under warranty. Rohloff hubs aren't cheap and you deserve a perfectly functional unit!
If I had to guess, I would wager that your hub is shifting into gear 11 (the high-range version of gear 4)temporarily during your intended shift to 4th, from either 3rd or 5th. I'd put money on an internal spacing issue or faulty shifting shaft.
From my understanding, Rohloff's shift into 14th during the 7-8-7 shift, because gear 14 is gear 7, minus the final reduction. It is the shift from low to high range (or vise versa), in addition to a gear change, that demands attention, otherwise the Hi/Lo coupling is under pressure and cannot release or engage, which turns gear 7 into gear 14 until the pressure is released. As mentioned earlier, in my opinion, any other odd behavior is unacceptable.