Bug Report: Multiprocessing bug

**Describe the bug**
When using multiprocessing the images generated have varying plot sizes and adding a lock to the plot function or plotting in a loop works fine.

**To Reproduce**
Steps to reproduce the behavior:
Plot multiple charts using
python multiprocessing.Pool
map, apply, etc

**Expected behavior**
The generated charts should be the same as the charts generated in a non multiproc

Start by reproducing the issue with Python multiprocessing.Pool using map or apply, then compare the generated charts with charts made in a loop or with a lock around plotting. Done means multiprocessing produces charts with the same plot sizes as the non-multiprocessing case; the issue provides no named files or tests.

Written by the indexing model from the issue text.