I fully understand you viewpoint. I also acknowledge your non-reliance upon GNSS as a sole source of navigation data (unlike some contributors for whom GNSS is considered adequate) - your approach being fully consistent with good navigation practice.
What is perhaps interesting is that the only complaints that I have seen, within this support community, relate specifically to the Navionics App. By definition, support communities only tend to capture issues or difficulties - and not tales of non-issue. That said, reports of issues are few.
I do have a potential suggestion. While using your iPad for marine navigation, turn off Cellular. Here’s why…
iPad and iPhone will periodically/automatically scan for Cellular signals. If Cellular networks cannot be found, scanning will continue in an attempt to find a serving network - using CPU and increasing battery consumption. It follows that Cellular network coverage is biased to land-based communications and may have poor, intermittent, or no coverage in some maritime environments. Combine this with sub-optimal device antenna’s, in sub-optimal positions, only combines to exacerbate the problem. If Cellular coverage is poor, your iPad may be needlessly expending processing effort.
iOS/iPadOS is not a pre-emptive operating system, but is optimised for low-power battery operation. CPU and processing bottlenecks, caused by other processes, may temporarily (for a few seconds) steal resources from a foreground process - such as your Navionics App.
Disabling Cellular will not impact the GNSS receiver (this being an independent element of the Cellular chipset), but will release resources for other more critical processing. I make no warrantees that this will fully resolve the problem, but it may be helpful. If nothing else, your iPad battery will benefit in reducing battery consumption in areas of poor signal.
