Also when in shallow my depth would read around 18-20 when I was actually in around 3-4 ft.
Friend’s new Helix 10 had similar. Graph wouldn’t show the echo so I read bbc and a bunch more things.
Here’s what I learned outside of the norms like is your ducer still level, etc.
Check surface clutter setting. If you are around 1 on a 1-10 setting increase it significantly and retest. In shallow and hard bottom this can be bad and a nightmare when trying to use auto chart live.
Since we’ve been back from our trip I’ve been able to reproduce the issue on my Onix 8si even with soft bottom. When running a setting of 5 I”m good. When I test at 1 it’s no bueno.
DI echos – to some extent this can be normal on a very hard bottom. I would try adjusting sensitivity and maybe frequency from 455 to 800. I’ve not tested but did see posts like this in my internet travels on the first issue.