I've a Login with salesforce functionality enabled in my application. When I generate a login oauth url which consists of app secret and ket and after sending a get request using browser It redirects me to a previously used cache instance url.

It should redirect to https://login.salesforce.com/?ec=302&startURL=%2{someurl}

but instead it's redirecting to https://myinstance.salesforce.com/?ec=302&startURL=%2{someurl} although I'm logged out of salesforce and this url only accepts my login credentials which are linked with my instance where as login.salesforce.com accepts anyone's login credentials.

if I use incognito window it works fine and I've even tested the oauth url using postman the response is a html file which has javascript function which redirects to login.salesforce.com/?ec=302&startURL=%2{someurl}
Is there anyway I can solve this issue or force my oauth url to redirect to login.salesforce instead of cached url.