Brown is usually earth. And unusual flashing and constant on/off instead of flashing can be a sign of earthing problems too.
The body of the light switch earths to the dash, so you can swap the spade connector for a ring connector and link it under the screw that holds the switch to the dash, or you can create a link cable with a male spade to take it to an earthing point elsewhere.
A normal ignition switch should have 3 connections (all live) and all earths should go to the body/chassis somewhere but sounds like maybe the indicator earth on your bus has been routed to the ignition switch rather than to the body.
The indicator flasher was originally a metal unit which screwed to a mounting by the fuse box so was earthed to the body that way. But modern ones are plastic and run an earth cable so there’s no ‘official’ place for the earth cable to run to. So maybe that’s what your extra brown wire is?
Hope that helps, I’m no electrician but I spent last weekend under the dashboard with a multimeter and now have lots of flashy lights so hopefully in the right direction
Sent from my iPhone using Tapatalk
