If you try to Run a query but have forgotten to define a prefix, Studio used to give back a nice message about an undefined prefix. Now it just says, "Something went wrong and we're not sure what it is." I spent too much time troubleshooting my connections before realizing it was a SPARQL error.
Thanks for reporting this; it is indeed a bug. I've created an issue for it internally, and we will likely have the fix for it out shortly.
Nice, thanks. Now that I think about it, it's larger than just the Prefix part. It's not telling me about basic syntax errors (like forgetting a period between statements). Hopefully that's a part of your fix, too. Thanks again.