Can't update/insert if html on asp.NET

I am migrating my sites from classic asp to asp.net. I am having an issue with any update/insert action that contains HTML code. It works on the asp site, which is on the same server, and the same database.
I’m getting a runtime error on the server. Has anyone had this issue and overcome it? I’m sure it’s something I’m missing but I’m out of ideas. Any help would be appreciated. Thanks in advance

For testing, I have simplified it to one field that is varchar(max). Sending <p>Test</p> errors out and sending ‘Test’ works fine. I have also tried as a text field, text area, and summernote text.

The error I see is in the serverconnectForm.js and is listed below

this.xhr.open(method, action + (qs ? (action.indexOf('?') > -1 ? '&' : '?') + qs : ''));
        this.xhr.timeout = this.props.timeout * 1000;
        Object.keys(this.props.headers).forEach(function(header) {
            this.xhr.setRequestHeader(header, this.props.headers[header]);
        }, this);
        try { this.xhr.send(data); }
        catch (err) { this._done(err); }