OP8 - Issue with scheduled power-on feature

I just bought a replacement for my trustworthy Op 8. I was planning on keeping it as a backup phone, in case my new daily driver gets broken/lost/stolen. I switched it off and left it in a drawer. The next day, to my surprise, i found it powered on. I turned it back off again, to find it powered on again the next day. Tinkering through the settings, I found a "scheduled power on/off" feature, which was set to automatically power on every day at 5:30 am (which I don't recall ever setting).

https://preview.redd.it/yoia3kyg2vhf1.jpg?width=1080&format=pjpg&auto=webp&s=b3fa936028e03cd7b8fbc8ca7e5ca330704ec6d4

Now it is when things become crazy. The next day, I checked on the phone to find it powered on again. Long story short, no matter if I disable the power-on setting or change the schedule, once the phone is powered off, it falls back to the M-S 5:30 am power-on setting. I tried to set a scheduled power-off to counter it 15 minutes later, but it doesn't work either; once the phone is powered off, it gets disabled. I don't want to factory reset the phone, the point is to have it readily available in case I need it, not spending 4+ hours setting it up from scratch, so the only thing that comes to mind is to keep it permanently plugged to a charger, so the battery won't discharge (I read somewhere it is harmful to store a device with the battery fully discharged), which is not ideal... any idea of how to fix this?

Thanks in advance.