Airdata.com, the same way I reviewed. I’ve got several of my Spark logs that are similar to yours, but terrible compass errors also.I have 4 batteries and it happens on all.
Where did you upload it to see the voltages?
FWIW, my Spark is now acting almost perfectly. I reset the AC, reset the controller, re-paired the RC with Spark, and all well. I am using an OTG wire with I7. I regularly brush a little contact spray on battery connector protectant.