Oh wow! Surf safely, Billo.
When I look at your spreadsheet, it looks to me like Billo nadirs later when she is breaking a bounce and but earlier when she is having a more regular cycle without a bounce. Maybe not always, but this is a pattern I'm seeing on a few different days at least.
Even Butters, for all of her late nadirs, still will nadir at +3 sometimes and then anywhere in between +3 and +12. Occasionally maybe even at +13 or +14! Like everything else with FD, it seems very little about it is predictable!