How your client retains added relays is really dependent on your client.
I think most clients now send a complete list of your relays when you hit the post/save button. It may take time for your client to find that latest list version but most seen to cache this information locally on your device so it's ready at startup.
Try adding nostr.mutiniywallet.com to your relay list. It's a blaster relay so is better for sending events (sends to all known relays) than receiving them. I use it to distribute my events far & wide. Add mutiny & post your updated relays