Cells skipped when 'Run All'

Over the past week or so, I have notice that Jupyter Notebook has started to skip cells when 'Run All'. There are no commands in place which should allow this. I have also noticed that it tends to skip the same cells each time. I only notice as I get an Error as some varible is not defined. I then have to go back and manually run the cells in turn, which in a large notebook is a real pain.

I am not sure if its because I am running the new version or not. I have managed to recreate the issue with a real simple example where I have 17 cells with: a = 4, b= 3, c = 5, ... , q = 4 in different cells. Then another cell adds them up. Every time it skips the same cells with m, o and p. (not sure if that is significant), and the execution order also appears jumbled up. I have added a screen grab of the failed Notebook.

My software versions

+ Python 3.7.0 (default, Jun 28 2018, 08:04:48) [MSC v.1912 64 bit (AMD64)]
+ IPython 7.0.1 -- An enhanced Interactive Python. Type '?' for help.
+ Notebook server 5.7.0

Has anyone else had this issue?


Reproduce the report with a 17-cell notebook assigning a through q, followed by a cell that adds them, using the listed Python, IPython, and Notebook versions. Observe whether Run All skips m, o, and p or produces a jumbled execution order; done means every cell runs in order and the final calculation succeeds.

Written by the indexing model from the issue text.