So my colleagues don't proactively do PR reviews, even when they're assigned to them, unless asked for the n-th time by me or the PM.
In the meantime other PRs get merged, I need to merge master in my branch, and solve conflicts every time so that it is eligible for merging.
Additionally, while reviewing, the requierements engineer realizes that there were corner cases not initially covered in the ticket description, so I get review findings about covering these.

Some people have reviews low in their priority list but it should be high

Should be discussed with manager imho.

Make a timeline depicting how the PR got invalid due to not being reviewed in time.

IMHO it's a grave workflow error when a PR for a ticket is open and the ticket gets changed after opening the PR...

Best would be a follow up ticket as the code is already written.

Used to have the same problem.

We brought it up as our biggest pain point slowing down development and decided to change it. Was easy to get managers on board (anyone who's taken a recent Agile class will have been instilled with the idea that shipping one thing fast is better than shipping two things slowly) and now the last part of our standups focus on completing PR:s, followed by a time slot where we are pushed to do reviews (often during a call so we can resolve concerns directly instead of posting a comment and getting an answer days later) without feeling guilty about not working on our own tasks.

This has in general lead our dev team to collaborate more, to spend up reviews. We work on fewer things at once and ship them faster, rather than doing individual work, and waiting forever to merge.