Yes, thanks, and I can't offer any insight from a TA perspective...

Yes, thanks, and I can't offer any insight from a TA perspective - at the very bottom of the learning curve myself. SHJ in particular does often puzzle me, though - there can often be very small volumes at the top of either side of the bid/offer, little apparent movement in price, and yet more substantial volume transacted through the course of the day. This pattern repeats more than on any other stock I own, and has been particularly prevalent during the recent rise in price.

As you point out, it appears to be the stubbornness of sellers that maintains the levels, and potentially very small trades that can move (or maintain) the price.