I'm new and experiencing the identical problem. Is it safe just to delete all such files?
No, talking shortly, no.
You should give us full name and path of that files.
No all files that can't be scanned are dangerous. In fact, I think only few of them will be, in fact, viruses.
Better is send the file (or add) to Chest and wait for further analysis.
You can also submit the file to on-line scanning. There are a lot of references here in forum where you can get the best on-line scanners.