1. If the Slow Aircraft setting was turned off it wasn't light related. What was your overlap setting? What is the SD card speed setting? If the overlap was high and your SD card speed was slow that will limit your maximum allowable aircraft speed to make sure that the framing limits mesh with the overlap requirements.
2. The aircraft should fly the same speed for all flights in the mission. If it flies 4.4 m/s in the first it will do the same in all subsequent flights. We will look into this because we have heard some other issues related to multi battery missions and the manual exposure setting. Are you manually landing or allowing it to land on its own? Sometimes there are some extra modes thrown by the DJI software and this will drop extra Abandonment Points which will cause the behavior you are seeing. If you let the aircraft come all the way back under automated control and just take over when it is time to land this will not likely happen.
Please email any pertinent log files to email@example.com so we can inspect them to see what might have cause the issues.
Thanks for the detailed reports. We hope to fix these issues in the next release.