I know you say it’s circulating fine, but have you actually tested the circulation pattern by staining the water? Add a drop or two of strong food colouring to the bath and watch how quickly it’s dispersed. Poor circulation is the only thing that makes sense.
But really, if you haven’t already done so, you need to get in touch with Support and see if they can come up with a reason for the issue that you’re seeing.
Your 124 ºF steak looks fine, and evenly cooked. Your 126 ºF steak is very unevenly cooked. If you were to take two (evenly) cooked steaks at 124 and 126 and put them side by side, you’d barely tell the difference.
So, see if you can find something that was different for your 124 steak versus your 126 steak; it might yield a clue.
Today I cooked at steak at 126F but a much thicker cut. I am so happy and suprised at how it turned out, I will try the same cut tomorrow at 129F to see if an evenly cooked steak was just a one off.
Use THICKER steaks! 3.5 cm (1 inch) is NOT a STEAK!
2’’-2.5’’ is a STEAK.
Keep the package away from the heater, and make sure there is enough room for water to circulate all around it. 130F, for 1.5 hours max, is plenty of time.