I asked Newtek about this and this is the answer
Airsend is an interface that is now almost a decade old and is not supported in any product that we ship (for over 5 years) and as such we are no longer supporting. Modern versions of Caspar support NDI natively.
So the fact is that Newtek wont try to fix this. From a business sense I understand it. But it means problems for at least Tricaster and vMix users because they have both just or will release a new version based on NDI 4.0.