First of all, thank you for this open-source python implementation of RatSLAM.
I tried to run the code on the "Kitti Sequence 00" dataset. You can see the video for another SLAM algorithm here that contains the ground truth.
I can see based on the video that the algorithm on the second turn, it rotated to right instead of left. Here is a result of the 450th frame: 
What can cause this phenomenon?
Regards,
Szilard Bessenyei