It's not Groundspeak's responsibility to fix other peoples' software. They do advertise when changes are made to GPX files and it's up to developers to handle them appropriately.
That said, the GPX format preference can sometimes get wonky. Go to your account settings & check the format. Switch it to 1.0.1, save, then set back to 1.0 & save again. That may get you back on track. But you may just be using outdated software that isn't getting updated when it needs it.