As per the What's New
document, Update 2 has introduced a 64-bit Linux data mover, so this would explain any potential difference in behavior after upgrading.
Looking at your system spec, your backup repository server clearly does not meet the minimum System Requirements
on the amount of RAM. In fact, 8GB was way below minimum requirements for 12 concurrent jobs even for legacy 32-bit data mover, and 64-bit data mover consumes twice as much memory due to additional performance optimizations we were able to add (which use RAM cache), thanks to the fact that 64-bit processes can address much more memory.
If increasing RAM is not an option, then a quick and dirty solution in your case would be to reduce the amount of concurrent tasks from 12 to 4 or so.