I was unable to reproduce the issue, as running your example on Presidio's demo site detected all the names you've mentioned (Karthik, Priya Sharma, Rajesh Gupta) on most of the NER models.

Maybe you are running on a different spacy model or different spacy version?

I would also recommend trying to replace spacy with transformers before training a custom model, see the documentation site for full explanations and samples.