Is this issue because of server error or plugin error or theme error?

Can I know how this issue happening as showing in the image? There is a breadcrumb issue reported for my website URL - like as showing in the screenshot. Can anybody tell me how this can be solved?

That’s a Schema markup error coming from your site’s breadcrumbs. That Schema markup may be part of your theme or it could be part of your SEO plugin. You’ll need to figure out which in order to troubleshoot further.