Heyo -- We'll have a few fixes for Raze Ult in the 5.05 patch. It likely won't make the patch notes since it probably won't fix every instance of this issue, but it should help. It will fix this situation, and we'll keep an eye out for other issues.
These fixes are specifically for when the rocket does zero damage. This won't affect situations where it deals some amount of damage, but it looks like it should deal more.