The shafts are breaking with the engine at idle while your are bleeding the injector lines?
WOW!
Don't jump to conclusions and pull the engine, unless/ until there is solid reason to do so. Right now that sounds like a shot in the dark. I can't think of anything internal to the engine that would cause the IP shaft to break, so it must be either the IPs or your procedures, ( no insult intended--just trying to isolate the cause...).