That doesn't look like anything to be concerned about.
As mentioned in post #12, it's probably just your VPS trying to lock onto any ground detail for position holding, but unable to because there's no recognisable detail.
It's important to understand the limitations of your equipment.
Your drone's height measurements are all done with a barometric sensor that measures air pressure and all heights are based on the power up location = 0 metres.
Setting heights...
Can you explain your reasoning why VLOS is not practical? It seems with your outcome, flying 1100 yards in close proximity to a hazard was not very practical. If your mission was to film surfers why didn't you go to the beach?