There was an issue where nodes would not reconnect after restart, fixed in IntersectMBO/ouroboros-network#4734
This could be identified by a test that is submitting transactions while restarting individual nodes. At the end of the test, there would be a check that all the nodes can see all the UTxOs created during test runtime.
The test would be using the "mainnet" local testnet, because the reconnection is unreliable on the usual local testnet with short epochs.