I also have an issue with RME driver, but it’s not the same one : in my case, it’s almost impossible to set it to 128 samples latency for recording. Doing so leads to an immediate comateous state of Cubase with an audio processing load of 0 and no more audio signal of any kind coming from it.
I don’t know if it’s also the case on your end, but I also often have to quit Cubase and relaunch it (with sometimes several attempts, after resettting the driver to 256 samples to get Cubase alive again). A screenshot of the issue here…