So I made so if the game starts a naval mine will spawn in a random place but if I add a second one it just disappears
Try using the clone function in order to copy your mine to multiple locations. I am having some issues with my phone at the time, but I can give you an example later.
Maybe this topic could help you out a bit?
Hi and welcome @Vigitel. I would recommend watching these videos, which I think can be really useful:
Maybe add both of them in the group and do affected object?