Current nightly build on Mac. Reproduced in safe mode. I did not test any other platform.

1. Open account settings
2. click Junk settings
3. ** observe that "enable adaptive junk mail controls" box is checked (enabled), AND "Do not automatically mark ..." and the address books are greyed out ... as if "enable adaptive junk mail controls" is NOT enabled
4. click the checkbox "enable adaptive junk mail controls"
5. ** observe that "enable adaptive junk mail controls" is still checked - it should have gone unchecked
6. click the checkbox "enable adaptive junk mail controls" (this is the second time)
7. ** observe that "enable adaptive junk mail controls" is unchecked and the address books are not greyed out
8. click a different setting tab, such as composition
9. click Junk settings

Actual results: "enable adaptive junk mail controls" is checked (enabled)
Expected results: "enable adaptive junk mail controls" is unchecked (disabled)

Amazingly similar to 1 year old Bug 1529443 - "Enable adaptive junk mail controls for this account" checkbox does not maintain state (tristate?) - which was never confirmed. But surely that bug hasn't been valid all this time

I don't see this on Mac nor Windows. The address books are active on point 3 for me. Tested with daily from 25. and the latest.

Also seen after creating a new profile on Windows 10 using try build.