Yes, the integration stores the username & the password until the next reboot to make it simpler to add multiple devices without re-typing the credentials. Each individual config entry (i.e., individual device) will only store a hash from the credentials that keep working as long as the username & the password remain unchanged.
I don’t have this device, but I haven’t seen this issue on any of my test devices that use the authenticated protocol, so it’s hard to say what could be the problem.
I went to 2024.2.0 and tada, it also discovered one of my new EP25 devices. I should have restarted Home Assistant, but instead I just plugged in the other 3 EP25 devices, then added them 1 by 1 by IP address (that I looked up in the Kasa app under Device Info).
Yay! I wasn’t a fan of the authentication for the first one I added. I’m glad it didn’t keep asking for authentication for my 2nd, 3rd, and 4th EP25s as I added them.
This was user error. My device had poor wifi signal and was dropping off because of that. After getting better signal to it, I haven’t had anymore issues even after unplugging it and plugging it back in. Thanks!