Juniper M5/M10 Midplane problems ??

Been looking at a M5/M10 box and have noticed its not real easy (unless I'm blind) to replace the mid-plane. Thus I'm wondering what people in the field have experienced with respect to mid-plane failures. 1. Bent or broken pins on the PIC side 2. Circuit failures My eval of this product is for a client and their infrastructure needs. Other bits of learned wisdom also excepted and encouraged :) Thanks john brown