rftools-1.12-7.13
Per title. The projectiles (usually blue skulls) will then wreck havoc as usual. There is also the client-side errors that's emitted right click to open the shield block.
https://gist.github.com/Fatmice/da7fb203bfa423366bc756cf9db97339

Thanks for the report. I will check it out soon

Actually there may not be anything I can do about this. Apparently the Wither uses the same function to check for projectile trajectory that I use to make sure players cannot notice the invisible shield blocks. So I guess this is just a limitation that will probably stay

Okay.