Site Collection Stuck in ReadOnly Mode

I ran Backup-SPSite and it completed without any errors. However, the Site Collection seems to be stuck in read only mode after.

When I go to Central Admin > Site Collection Quotas and Locks, all the options are grayed out for the Site Collection. I cannot change the status to "Not locked", or anything else. This only happens for the one particular site collection. I am able to update the lock status for any other site collection on the same farm. I am a site collection administrator.

I tried using PowerShell with the following commands. However, it has no effect.

$site = Get-SPSite -Identity <SiteURL>
$site.readonly=$false (Does not output any errors)
echo $site.readonly (Still outputs true)

I am able to change the lockstate to "No access" using Set-SPSite. But if I change it to anything else, it sets to Read-only.

The Content Database is not set to read-only.