Missing bones in skeleton problem after upgrading to 4.9

I’ve just upgraded to 4.9 and every time i launch my project in the editor i get this message:

57183-1.png

When i try to open the skeleton / mesh i get this:

But if i drag the Skeletal mesh to the world it shows up normally and in-game works like it’s supposed to. What can i do to resolve this? Thank you.

I got this error too… however, I just opened up both FirstPerson_Skeleton and FirstPerson_SkelMesh, then saved them (even though no changes were made) and it went away.

I have been getting this as well!