Private wifi address: have to keep disabling/reenabling every few hours to connect to home WiFi?

I have an iPhone and a MacBook, and have wireless (4G) internet router in my house.

Every few hours or so, one of the devices will disconnect from the wifi and then it won't let me rejoin again. It asks me to enter password, and then fails.

If I switch private wifi address to fixed, it will let me connect again. Then usually a few hours later, the opposite happens: it disconnects, and will only allow me to rejoin when I turn private wifi address off.

This happens on both my phone and MacBook at different times.

Does anybody know how I might fix this?

I used to rarely have this issue, but I think it only became a daily issue when I updated to IOS 18 and Mac OS 15.

I have reset network settings for both devices and it still happens.