Acronis True Image only creating incremental backups
I have Acronis True Image running on two Macs, an iMac and a MacBook. Both use a WD MyCloud NAS on my local network (iMac is connected via hardwired Ethernet, the MacBook by wireless).
On the iMac, scheduled backups run every night with full backups every 6 or 7 days. Absolutely no problems.
On my MacBook, I only ever see incremental backups. For the last 12 nights, an incremental backup is created every time. No full backups. The MacBook backup file is about twice a large as the iMac backup (268 GB).
So my question: Why is Acronis creating incremental backups and never a full backup? And why does it work just fine on my iMac? Both are running the same OS (Catalina 10.15.4). I've also created a recovery disk for each, if that makes any difference.