Mulberry problem

the ancient (I was told 300yrs plus) mulberry in the garden is producing strange feathery fruits. It has done this before- they grow out and then wither and fall off. I’m including two photos from the same tree- one (the lower one in this post) shows the mutated fruit where the segments grow apart and the fruit fails totally, the other is much greener and compact and will, I hope, turn into proper mulberries. Does anyone know what’s wrong with the tree? I have no idea what this is, and the tree is big enough for it to be annoying but not ruinous — but if it’s in any way dangerous for the tree I’d like to stop it now.