I've got a governor in a settlement who has 2 x +1 law modifiers (aged retainer and Office of Praetor) and 1 x -1 law modifier (popularis)

Yet when he enters the settlement, it has a -1 effect on law in the settlement (from +15 to +10)

There are no other officers in the settlement and I've checked very thoroughly for any other modifiers. I'm not sure if it makes a difference to governing cities, but he also has imperium.

Do the negative law modifiers have a bigger effect than shown? I'm I missing something?
Just when a governor has a net +1 law modifier (and a -1 to unrest modifier as well), I expect him to have a positive effect on order in the settlement.

Searched like hell and couldn't find anything about this on the forums.