2.7 is your m851 offset I assume. But probably needs to be negative instead of positive?
Could also be relative/ absolute motion potentially.
I had this problem a while back. I fixed it by sticking tweezers in the female socket on the printer. I fiddled with the pins around until I got it to connect. Also, try downgrading to 0.16.0..
Everyone, please don't just blindly stick tweezers into any kind of sockets in the hopes it will solve connection issues. At best it will do nothing, at worse it will break the printer or even start a fire. And I don't see how downgrading to an by now pretty outdated OctoPi 0.16.0 can help here either, considering that the OS image isn't the thing talking to the printer.