well, a lock file is used to stop tasks from occurring simultaneously that must occur mutually-exclusively with respect to time - they cannot run at the same time. The idea for a backup program locking itself is obvious - it makes no sense to obtain a backup snapshot of the same state of the vast majority of your files, if not all of them, twice.
the regex (short for regular expression) in the [exclude] section seems to be selectively backing up everything except thumbnails in any directory under /home (which can be generated dynamically later and would only be bloat in the backup), temporary files for the user, and a couple other things that may be unique to your system.
the [dirconfig] section seems to be marking dynamic system directories as also being excluded from the backup
finally, the [general] section contains information about where the backup should be stored (target), the lockfile, and other options that you can probably configure the software with.
If your problem is that sometimes the backup does not run, is it possible that it is already running? That is the purpose of the lock file - the program should create the lock file if it does not exist, and if it does exist, the program should exit. When it is done running, it should remove the lock file so that the next time around it can run as expected.
How often is the backup scheduled to run?
The community here can better assist you if you answer the questions, and determine exactly what program we are talking about.