It looks like your Ground Reference image was not detected which is why the elevation processing was off. Our system will only find ground reference images that have Absolute Altitude values within the range of -3 and 3 meters. This might have something to do with it being downscaled to .25. I bet processing it at native resolution would work.
You flew at 105-ish meters AGL. GPS derived altitude values are notorious for being way off so that value basically got subtracted and you ended up with negative elevations.
Again, this is likely an issue with takeoff tags not surviving the downscaling process. We will look into that.