Laptop locks immediately when unplugged after period of inactivity. Acer Aspire 5.

This is a subtle one: I have a good grasp of Windows Power Options, and have had many laptops over the years, but this is what happens on this Aspire 5:-

Stay awake and unlocked set to: 4 hours of inactivity plugged in, 30 minutes of inactivity on battery. So that's all normal.

But if it's been plugged in at my desk and inactive for 45 minutes, if I pick it up to use it and unplug it, it locks the screen. I know that this is following the strict logic of "I've been inactive for more that 30 mins and I'm on battery, so therefore I must lock/turn off display", but that's not how laptops normally work. This problem is subtle, and people and AI usually respond with some basic instruction about Power Options. Please don't do that and re-read.

Normally (with other laptops) you would get 30 mins from the unplugging activity, so the action of unplugging is counted as an activity.

It's annoying because it will sit there unlocked for hours, then when I pick it up it locks! Which is annoying.

Any help appreciated.

Thanks

Mark