When I used IBackupBot to restore the archive, I was prompted that the space on disk C was full, but there was still 20G on disk C, and the computer was not poisoned.
That's because you installed the software before and then uninstalled it. Over time, a large number of disk fragments will be generated. Although you still have 20G, these spaces are not continuous, so you can't store some larger files. You can download a Tencent computer housekeeper, which has a system disk to slim down and merge these fragmented intervals.