HereFlow Flight Issues

I followed the inflight calibration directions for a HereFlow: Optical Flow Sensor Testing and Setup — Copter documentation and linked the EKF source to switch to transition to using optical flow in flight. After the switch to optical flow the vehicle seemed to hold position ok but after 15-30 seconds of slow moving it rapidly accelerated. This happened twice in a row. I did a hand calibration data collect and the IMU and OF values look pretty well matched to me so I’m stuck. Any suggestions about what could be causing the issue?

The flight log was too large to upload so here’s a link:

log_1_handCal.bin (985.1 KB)