Blocks Broken Rhino 6.4.18107.1041

When I paste an object into a block, everything outside of the block becomes visible, and the block edit window blanks out so I can’t exit the block. I have to use “unlock” to work the file again. then there is an exploded instance of the block on top of the original block.

I updated Rhino to 6.4.18107.1041 today.

If I role back to the Rhino version on
will I still be able to open files created/saved in version 6.4?

Edit: I can use “Add to Block” for the time being