Reasons for a script tag to throw an error

Question

I'm currently using the following script (with AlpineJS directives) tag to check for an ad blocker. However, regarding to user feedback, this sometimes results in a false positive. What could be the reason for this?

<script async @abort="ad.blocked = undefined" @error="ad.blocked = 'VisX'" :src="`https://s.visx.net/tag.js`"></script>