From n1ck0's support topic:
The Events Calendar shows "Untitled" on some pages.
This seemingly means that The SEO Framework can't access the CPT/CPT-archive title through WordPress' API.
Thanks @sybrew. Currently this only happens to us on the browser title of the default month view page. Default list, day, photo and map work fine.
Thanks so much @sybrew. 2.9.4 fixed the issue. Cheers mate
I am still having this issue on the latest version of the SEO Framework and The Events Calendar.
That plugin's hijacking the WordPress query (without setting the page name), instead of correctly registering the archives.
I tested a few SEO plugins with their monthly archives, and they all show different issues with the titles.
I can't open an issue on their Github, so I'm afraid you'll have to resort to their support forums.
Okay, thank you @sybrew for looking into it.
It seems the plugin's setting "noindex" for its event archives. This is good, because you can safely disable the post type without having to worry about the mixed titles for the /events/ endpoint:

Note that the option will disable TSF for the single events, too.
This fixed the issue! Thank you!
Most helpful comment
Thanks @sybrew. Currently this only happens to us on the browser title of the default month view page. Default list, day, photo and map work fine.