Sometimes(!) the home screen does not load after logging in

Sometimes when I log into Rocket.Chat, the home screen does not load. There is the channel list on the left and on the right there is a white screen where the 3-dot animation keeps looping. When I click on a channel, the home screen loads. Only when I then click the channel a second time does the channel load. It's as if the home screen loading was waiting on some event to continue which in some cases does not fire until the user interacts with the client. Or perhaps it fired too early?

The issue occurs on Rocket.Chat 0.74.3 as well as on the current develop branch, running on Docker on GNU/Linux with MongoDB 4.0. I have maybe tested this about 30 times on a Docker build of the develop branch. It happens on both Firefox and on Vivaldi, with both regular login and SAML login, but it seems to be happening more often on Firefox than on Vivaldi and more often when using SAML as compared to regular login, again pointing to a timing issue.

I couldn't find anything useful for debugging in the Firefox Web Developer tools and there isn't anything in the Rocket.Chat logs either (besides the regular SAML output when SAML is being used).

I have no experience with meteor development, but if someone would be kind enough to give me some pointers on how to debug an issue like this, I'd be happy to look into it.

Start by reproducing the login flow on the develop branch in Docker, comparing regular and SAML login in Firefox and Vivaldi. Inspect the browser developer tools and Rocket.Chat logs while the white screen and looping animation appear. Done means the home screen loads after login without requiring channel interaction.