Changelog entries in wrong position, problems keeping track of version

#### Environment details

GitHub release-please-action v4.4.0

#### Steps to reproduce

Release-please for some reason keeps adding its changelog entries as the 2nd position in CHANGELOG.md as opposed to the first in a project of mine. This has been going on for a long time for this project, and I've always had to fix it up myself.

Here's an example PR showing the problem: https://github.com/scop/bash-completion/pull/1298

For some reason, release-please added the section of 2.17.0 entries _after_ the 2.16.0 section, i.e. between 2.15.0 and 2.16.0.

I've had to correct that manually myself, as in https://github.com/scop/bash-completion/pull/1298/commits/22c646f57a9d6274ab9328f02499993ce37f2952

Additionally, after the 2.17.0 release, release-please seems to have lost of versions -- there have been no commits after 2.17.0 but there's a PR open already for 2.18.0 containing a lot of changes already released for older versions: https://github.com/scop/bash-completion/pull/1494. That block of entries is also incorrectly positioned between 2.16.0 and 2.17.0, should be after (above) 2.17.0