Incremental backups takes very long

Hello Gitlab Community,
I am currently trying out to backup a very big Gitlab instance using the built-in backup too. Since there is a lot of binary data stored on the instance I need to do incremental backups to save some time. After my first full backup, which took half a day, I triggered the first incremental backup and was surprised that its very slow too. Even tho the data hasnt been changed. Is is expected that a incremental backup is taking nearly as long as the full backup or am I doing something wrong?
Thanks in advance.