I have 2 cocker spaniels who are brilliant with everyone including children and other dogs. One is the mother of the other as I bred a litter.
Previously I had a cockapoo with major problems, guarding, very attached to my husband, dog would chase you out the room to keep OH with it alone.
Why? Warning signs were there, as when I picked the cockapoo up as a puppy it was trembling all over. Had not been well socialised. Realised this when I bred my litter and tails were wagging furiously when new people picked them up. Puppy should be confident in your arms, wriggly, and chewing at your clothes. That's a confident well socialised puppy. Preferably bred in the house as then they will be confident with household noises, like the TV, washing machine etc. Sharing this to help you, if it's timid walk away
I wish I had known this