make no sense to backup I think, as it is basically a FIFO (first in, first out) bucket for interprocess communication (sharing information between two or more running processes). If you restore a named pipe, what will the receiving application do with the bucket of information from the time it was backed up? Named pipes only make sense as applications are using them, not weeks or months later when you need to do a restore.
Are you given a warning, or a fatal error? (i.e., do you get your backup or not?)
I looked at the issues reported
for mintBackup, and this one isn't there. It would be proper for mintBackup to issue a warning on encountering named pipes, but it should continue to make the backup and ignore those files. If it isn't doing that, perhaps a bug report is in order.