Hey guys, I finally solved the latency problem and did not need to replace my PC. I installed a USB 2.0 PCI Express card to create an exclusive USB bus/hub to hook the MPC Ren and it is working now. It is difficult to understand if the problem was caused by the incompatibility with the hybrid USB 3.0/2.0 bus from my PC's motherboard or not having enough bandwidth in the bus itself, that was shared with other USB devices. The fact is that this product solved the problem:
https://www.amazon.com/gp/product/B002R ... UTF8&psc=1I bought this model because I needed a low profile board for my SFF Lenovo PC but I am sure that any other USB 2.0 board will do the trick.