ipcluster won't start in a certain directory

There is one directory where when I try to start ipcluster, I get the following:
>ipcluster start
2021-04-23 10:06:33.597 [IPClusterStart] Starting ipcluster with [daemon=False]
2021-04-23 10:06:33.597 [IPClusterStart] Creating pid file: /home/zach/.ipython/profile_default/pid/ipcluster.pid
2021-04-23 10:06:33.636 [IPClusterStart] Starting Controller with LocalControllerLauncher
2021-04-23 10:06:34.638 [IPClusterStart] Starting 8 Engines with LocalEngineSetLauncher
2021-04-23 10:07:05.411 [IPClusterStart] Engines appear to have started successfully
2021-04-23 10:07:08.690 [IPClusterStart] ERROR | IPython cluster: stopping
2021-04-23 10:07:08.690 [IPClusterStart] Stopping Engines...
2021-04-23 10:07:11.694 [IPClusterStart] Removing pid file: /home/zach/.ipython/profile_default/pid/ipcluster.pid

This is on both my local and remove Ubuntu machines. Here is some version info:

local machine
ipython version 7.22.0
Python 3.8.5
ipyparallel 6.3.0
ipykernel 5.5.3

remote machine
Python 3.6.9
ipython 7.16.1
ipyparallel 6.3.0
ipkernel 5.4.2

Things I have tried:
copying directory
restarting
upgrading everything
deleting ipython pid and engines.json files
ls -al to find files in the problem directory that might cause an issue.
deleting __pycache__

It was working well before today. Last tried several days ago, when it was working. Unfortunately the directory that is not working is the one I always use.

Start by reproducing the failure with the `ipcluster start` entry point in the reported directory and compare it with a directory where startup succeeds. Inspect the startup output around controller and engine launch, then verify that the cluster remains running and the pid file is cleaned up only when stopping intentionally.

Written by the indexing model from the issue text.