There is an issue with usb-serial devices on RC1 as reported by @Andrew_Rowe, @davorf and I experienced it on Windows 10 and Raspberry PI (using openhabian 1.5): the serial items (zwave controller and RFXcom for me) keeps reinitializing on openhab level, it is fine on the command line (using lsusb, dmesg etc..). It was causing very high memory and cpu usage and even using swap, the pi was unusable after a few hours.
Switching to latest snapshot, for me it is 1774, fixes the issue