Supporting Planner - what is going on?!?!?

So we've got several of our major workgroups now using Planner for action items

Today, one user when in and was browsing the Planner on their phone (mobile web), and all kinds of emails were triggered.  He says he wasnt doing anything just looking, and then all the sudden about 30 emails was triggered saying he made all kinds of updates and changes to several tasks (at the same time).

If you look at the tasks, in this screenshot below, it says he re-assigned a bunch of tasks, but the task assignment didnt actually change, it is all just posts made in the "Comments".

Now all of the task emails are in Portuguese (for everyone).  The Group Language setting is English (???)

And of course since the notifications for Planner are crap, all of these senior execs just got blasted by all of these portuguese emails....

I'm really not sure where to even start supporting this, cause everything looks right and set up right.