Hypothesis caching the same post title for all annotations on a single site

### Steps to reproduce
1. Annotate _any_ page on https://boffosocko.com
2. View https://hypothes.is/search?q=url%3Aboffosocko.com%2F*
3.

### Expected behaviour
I would expect the titles of the various annotated posts displayed on H to be that of the <h1> tag on the annotated page or some other logical name based on a parsing algorithm.

### Actual behaviour
The titles for almost all the annotations on my website (since 2016), regardless of the page they're on, appear to be the incorrect title: "Top Ed-Tech Trends of 2015: Indie Ed-Tech". The few exceptions seem to be the self-hosted .pdf files on my domain/storage that I've annotated.

### Browser/system information
This appears to be browser and OS independent

### Additional details
The only post on my website related to the title which appears seems to be https://boffosocko.com/2020/05/16/top-ed-tech-trends-of-2015-indie-ed-tech-audrey-watters/ which contains copies of the annotations I made on Audrey Waters' page. See: http://hackeducation.com/2015/12/21/trends-indie#annotations:soppjJeoEeq9gccaKJdTtg

Some time around 2016 Audrey disabled annotations on her site (due to abuse, though it appears she's since re-enabled them?). Is it possible that the H client has somehow cached the title of her post and is somehow mapping it as the title for all of the annotations made on my site? Having looked at the pages which have been annotated on my site, there's nothing hiding in or related to the the meta data or rel="canonical" links that would indicate that they should have the titles that H is finding for them.

(originally published at https://boffosocko.com/2021/02/21/hypothesis-caching-the-same-post-title-for-all-annotations-on-a-single-site/)

Reproduce the issue by annotating pages on boffosocko.com and viewing the Hypothesis search results URL provided. Compare the displayed titles with each page's h1, metadata, and canonical links, then determine what causes the old Audrey Watters title to appear across annotations. Done means the affected annotations show the correct page titles or a documented parsing result.

Written by the indexing model from the issue text.