I wonder if it's related to the memory "issue" with their client, where exceeding 1TB/1 million files, a manual edit of the .ini file to bump the JVM memory allocation is necessary. I remember reading somewhere that it has to do with CRC checksum calculation for all the files? I've had to change the setting multiple times (currently at 8GB for ~8TB/1 million files).

https://support.code42.com/CrashPlan/6/Troubleshooting/Adjus...

Hm, maybe give Borg a shot. For initial backups it's not exactly the fastest thing, though much better after that.