One change that might help EditGroups stability would be switching from the Toolforge shared Redis to a local Redis service. This is speculation on my part, but I feel that there was a correlation between reports of connectivity issues with the shared Redis instance and the rise of tools attempting to use it as the data store for Celery workers. Moving to a local Redis would eliminate noisy neighbor issues with the tool's view of the service.

That's a move I have already done, and it did help with making the service more stable indeed.
The remaining issues I am aware of:

• Celery workers getting killed, probably because of memory usage, meaning that revert tasks get interrupted. I have played a bit with the concurrency and memory allocation settings to make this happen less often, but solving the root cause of the problem would be better
• A need to migrate out of EventStreams to recent changes polling (I guess?) to make it possible to deploy the tool on other wikis (for instance Wikibase.Cloud)
• Need for ongoing care for the tool to make sure it stays in sync with the wikis (if it stays out of sync for longer than what the EventStream covers, we miss edits)
• Various other issues as recorded on the issue tracker: https://github.com/Wikidata/editgroups/issues