Hey @Vidula Khanna​ 

I found a workaround, I created a job that run the notebook. ( with cluster spec and not with existing cluster - which cost cheaper)

I think when a notebook is attached to existing cluster a lot of state of it saved which fill the RAM or there is some mechanism that starts to work on allocating memory to this and any other notebook that might come ,

When i run the notebook from a job, the memory being used was cut down by half and the run finished without any errors.

But for sure, this error is caused by out of RAM: link here