While I love the JVM, and I also think it's one of the better runtimes in terms is backwards compatibility, there have been breakages. Most of the ones I've dealt with were easy to fix. But the ease of fixing is related to the access to source code. When something in a data stream is broken, be it an MP3 or a JPEG, I guess you almost inherently need special tooling to fix it (realistically). I imagine that with an SVG it'd be easier to hand-fix it.