First off: thank you for this ingenious plugin!
I run it on 4 WordPress sites, 3 of them run smootly, 1 is giving me headaches.
Tried deactivating all unnecessary plugins, without result.
I have separate jobs for backup up DB and FILES. The Check & Optimize DB worked fine from the start.
Running the DB backup jobs seems to 'hang' at the same table at the 'dump' command.
The table belongs to Simple Download Monitor (wp_sdmon_details) and had 139000+ records.
Cleaning up these tables (when SDM is set to detailed loggin the table gets 'large' really fast as it logs all details from each download) solved it! The backup DB jobs runs smoothly now (size of the DB decreased from 17Mb to 8Mb)
I think it has more to do with the number of records in a large table, rather than the plugin itself.
Also: When hovering over the log entries, the 'used mem' and 'max mem' never were near the 'mem limit' (10Mb, 18Mb, 104Mb).
Maybe this helps you in working towards a solution.
I am happy to (re)test things for you if you want.
Still struggling with the FILES backup, I will do some futher investigation and post a new thread if I find something new that might help.
Keep up the good work, no matter what others say (sometimes even impolite)!!!