score:1

Accepted answer

Try rearrange the order of your route and also add exact

also in your code path='companies/:slug/forms' is missing a /

<Route exact path='/companies/:slug/forms' exact component={Forms}></Route>      
<Route 
  exact
  path='/companies/:slug' 
  render={(props) => <CompanyDetails {...props} isAuthed={true} />}
/>

If above doesn't work, try add / to your link in CompanyDetails page

<Link to={`/${this.props.match.params.slug}/forms`}>

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