I have noticed that sometimes when I reload my game, the following happens:
- Auto-Building does not work despite being on.
- When I toggle the button, it keeps being on, with a sound cue telling that it has been turned on -> seems like the state has been represented the wrong way before.
- After actually turning it on, another highlight area gets placed over the existing one, effectively reducing the opacity. Turning it off again will only remove the most recent visual area, not the previous one.
- This effect can stack, causing multiple visual areas to overlap and hindering the overview around my player.

Even after several times of reloading the game with either Auto-Build on or off, I was not able to replicate the behaviour which leads to that state inconsistency. Sometimes I inadvertently managed to reduce said stack somehow, but I cannot tell how. Might be coupled with actually restarting the game though. Disabling and reenabling the mod resets this issue.

EDIT: I should mention that I am regularly disabling/enabling the feature during my gameplay, so I might as well have saved and closed the game with both states alternating every now and then.

Yes, this is a problem, if you update mods with autobuild enabled.
The autobuild gets switched off by the update, but the visual area remains and can't be accessed anymore.

The only way to workaround this atm moment, is to lower the opacity for the second area to don't have a double amount applied.
It might help to remove the mod and load the save and see, if the area is gone. If yes, you can readd the mod. I didn't test it though.

I fixed that as contributor for this feature:
https://github.com/mspielberg/factorio-autobuild/pull/6
But it is not released yet.

This should be fixed now