From Kevin W elsewhere on this board:

"Investigators immune to being arrested are still immune to being arrested in Innsmouth. I had my reasons for ignoring the 'immune to delay' stuff in the jail, but that's different from being arrested in the first place.

Avoiding being arrested in Innsmouth is an Evade check. Sorry for the typo there."

Looks like that 10% finally came up

Enjoy your fleeting victory, forces of good!