I don't think it's a "you problem"; I've been having the same issue lately, although just occasionally. Started after the 0.18 Lemmy update so it's probably either a problem with that Lemmy version, or an infrastructure change Beehaw did around the same time (haven't logged in to my other Lemmy accounts in a while so dunno the problem exists on other instances too.)

Jerboa has been logging me out constantly to the point I'm considering trying some other app. Even kbin PWA has been working better for me in this regard.

I use Kbin on Firefox mobile and desktop - mobile I am logged out fairly often, but desktop rarely. I wonder if it's a cookies setting? Can't quite recall if other websites have similar workings as I use a couple browsers.

For lemhaw I just use Jeroba and connect. Jeroba I was logged out of during the upgrade but connect I was logged out of after.

I think it's mostly concidence and Firefox cookies protections

As @interolivary said, it's not a you problem. It sounds like you're using the PWA for Beehaw since you click an icon to open it. I've had this same problem on mobile using PWA (Chrome and Firefox) but not with desktop browser. I've also not seen this on the mobile apps I'm trying out (Voyager and Jerboa). From the symptoms it seems like closing a PWA session clears the browser cookie that's being used for session persistence.

Try just using it from the mobile browser; I have not seen this issue it on Chrome or Firefox on Android and I expect that Safari on iOS won't have the problem either.

Same issue here with beehaw PWA created by chrome. I deleted and reinstalled the PWA but the issue remains. If I close the PWA it logs me out.

My lemmy.world PWA is doing the same thing, so it's not just beehaw.

I've been using the voyager web app too and it stays logged in.

I've been having the same issue always with jerboa app, sometimes with Firefox on my phone, and right now I'm able to login with Brave on my phone.

You're not alone.