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You need to change your urdf to account for the fact that the optical frames are now all upside down, which will fix the sign problem.

The calibration tells you that if it can't find the wall start by lowering the default calibration so that it will find the wall.

If the TurtleBot does not successfully return to facing the wall before executing
the next rotation the data will be incorrect. This can be caused by too big of an 
error in the existing parameters. If it under rotates, increase the odom parameter and 
retry. If it overrotates lower the odom_parameter and retry.