This perhaps is along the lines of an answer:
https://www.andlil.com/forum/modification-dans-l-api-d-ig-lors-de-la-connection-t14293.html
Essentially double-tokening when there are multiple accounts.
I'm having the same problem. It works a couple of times, then the error code. Refreshing the login doesn't seem to work, but the companion does. Then eventually the login will work again