This site helped to resolve IPC wait event : Postgres checkpoint tuning | Tembo Docs
You have to adapt the checkpoint_timeout within the max_wal_size.
If the max_wal_size is 8Go then you can increase the default value of checkpoint_timeout (which is 5 min).
For big database with big wal size, you need to increase the checkpoint_timeout to avoid IPC wait event on the Buffers.