Old backups are deleted automatically according to the rules defined in the backup options. Read "Automatic cleanup rules" section in the user guide: local backups, backups in Acronis Cloud.
The backup menu option "Delete", that has always existed in the program, removes a backup completely, with all of its versions.
Acronis software may give errors, freeze or produce other undesired effects when there are issues with parts of the computer environment it operates in:
Disk partitions, file systems
Mapped drives are not listed/available in GUI (e.g. as the backup source/destination) or backup via acrocmd command line tool to a mapped drive fails.
Acronis products support Advanced Format disks
The RAID is detected as separate drives
File systems supported by Acronis True Image in Windows and Mac environments