Percona 5.7.24 : How to fix disk slave storage full
#sql files are temp tables generated by ALTER and other maintenance commands.  You will need to find what that command is.  At that point, you will probably find that it is in a tight loop, either spawning off process after process, or crashing and restarting.

Other clues:  The table name (for many of them) includes "ib916".  The table is about 7GB in size (disk footprint).