@IkerAriz, probably the best option is to turn on Slick-C profiling when it starts getting janky, do whatever operations are showing delays for you for a few minutes, and then turn it off and send us the profile. If there is a relation between the memory use and the jankiness, then that could point us in the right direction. You can access the profiler controls in the Macro -> Slick-C Profile submenu. In the meantime, I'll re-run some of the memory tests with a project setup like you described, to see if I can spot anything I've missed.
I see from one of your previous posts that background tagging is disabled, so there are a few things that can block the main thread with that. After the profiling, it narrow things further to see if that makes a difference.