I don’t know the relevance or if it is coincidence but…
In the past I would start a genesis node and then add more nodes using
~/.safe/node/sn_node --hard-coded-contacts '["220.127.116.11:12000"]' --skip-igd
It never caused issues.
Hard to remember exactly but it seems that around the time I needed to start using --genesis-key the nodes started timing out shortly after joining.