Microsoft Forms survey gets hundreds of illegitimate form captures

I have been using Microsoft Forms for years and had no issues.

I recently set up a survey and promoted the usual ways - email, Twitter and LinkedIn.

I was amazed one morning to see over 500 entries. However, upon inspection, the vast majority were random, dodgy gmail entries.

So I cloned the form and so far have only shared it on LinkedIn with only 9 engagements so far on that. Yet I already have over 30 weird entries again.

Any ideas why I am getting these false entries and how to stop them?