Backup and Migrate doesn't work

I have installed this module on my site two weeks ago and added one scheduled backup. But I see that it isn't stable.

When I try to make a "Quick Backup" and download it, the module just does nothing *most of the time*. But sometimes, I'm able to start a download. Same goes for my scheduled backup. I set up a weekly backup and when I look at the backups taken, I see that it has already missed the schedule last week.

Here is the export of my scheduled backup:

array (
'schedule_id' => '1',
'machine_name' => 'weekly',
'name' => 'Weekly',
'source_id' => 'archive',
'destination_id' => 'scheduled',
'copy_destination_id' => '',
'profile_id' => 'default_plus_email',
'keep' => '30',
'period' => '604800',
'enabled' => '1',
'cron' => 'builtin',
'cron_schedule' => '0 4 * * *',
'type_name' => 'schedule',
)

The uncompressed file size for a backup is around 30MB. I also tried using compression but the result was the same: it worked once or twice and didn't work other times. Clearing the caches didn't seem to help. I also tried reinstalling the module to no avail.

Note that it managed to do one scheduled backup so far.

Backup and Migrate version: 7.x-3.1

Any ideas? Are there any other modules that does this? Drush is not installed on my shared host, so that doesn't seem to be an option.