Reported by Noel: When a user logs into the app, they are directed towards /main/home and the home page will, in turn redirect to /main/home/dashboard or elsewhere as necessary.
The problem with this is that if a navigation happens before the home screen is loaded, the focus will be brought back again to the home tabs once loaded.
This can be tested easily with upsell alerts, pressing "upgrade" as soon as the message appears (and before the home page is loaded completely). But it's probably relevant in other edge-cases, so it should be fixed holistically rather than making a patch for this particular use-case.
Considering that this is not a regression and it's likely that it was already happening, I'm leaving this for 4.2. I have tried to fix it but it caused other problems, so for now I'll leave it here. Here's the wip code: https://github.com/NoelDeMartin/moodleapp/tree/MOBILE-4081-fix-tabs-loading