Few things you can try and take notes.
First disable bt on your phone and check in which situations on/off switching happens. If it doesn’t anymore - it’s media stream from phone, notification or something similar.
Second, take note if it comes when you’re in quiet and turn the water on, and then you can’t hear the water, or is it the other way around.
For first one, I’d reduce noise cancelling in quiet.
If your quiet is too loud, then check expansion.
Check means - tell your fitter the exact description and they’ll check, if they don’t have a clue, then use terms from here.
If you’re just annoyed with abruptness, note that and ask fitter to make autosense switch slower. (eg I have mine to fastest because autosense switches to noisy situations when I turn thw water and I don’t want to not hear anything for a few seconds until it comes back)
Or tweaking noisy situation.
For that, you should stare at my phonak app in hope you’ll catch it when it switches and see what exactly it says. For water running mine switch from quiet to noisy, and since it is not objectively noisy, I can’t hear until water stops.
I can’t remember if there’s a way to make the noise program anything less sensitive.
For big noise or whatever it’s called, sensitivity can be adjusted, but for regular I think not, but maybe noise cancelling could use some tweaking.
It could be something else of course. As you can see, even if you have described, it’s not precise enough to pinpoint it. We all can make wild guesses but only your fitter can see the options and probable suspects.
But make notes - what is the base situation, what happened noise-wise what HAs did. Not trying to remember later, but write down immediately when it happens
You might find out that there are several things/situations. I wrote some, and all could result in ‘autosense switches on/off’ type of description.
Btw actually autosense is always on, it only switches between its programs. I mean, it doesn’t shut off, but some change in its programs could result in you hearing worse.
But precise notes could help a lot. That’s main takeaway.