Realms not saving backups from more than 2 days ago

When trying to restore a backup for my Realms server, I noticed that my backups went back to two days before, and then there was a huge gap, and the next backup was over a month old. I tracked this behavior over a couple weeks, and it has persisted – backups older than 2 days are erased, except for the same three backups that are now a month and a half old. I have attached a screenshot of my backups screen so you can see the problem.

At this point, if I want to make sure I have a backup from a week ago, I have to download one manually every night. If there was some way to delete those older backups I would, but I have no way to do that.