I think you need to trigger Play From Start in timeline
You use one MID for any spawned decal, so I think if you fix Play From Start, you will see that every decal starts to fade in hen you spawn new decal
so… 3. To make every decal fade in on spawn you should use different MID for each of them and start fade in animation accordingly. It is possible if you make BP with decal, start timeline in decal BP on begin play, and spawn that BP on hit. I’m not sure but it may be expensive solution…