Please do the following. Please finish and save results from step 1 to post here before proceeding to step 2.

Step 1: https://support.apple.com/en-gb/guid.../mchlp1698/mac

Step 2: https://www.ikream.com/reset-dns-or-...jave-32817/amp

Step 3: Repeat step 1 and see if DNS results are now different after completing Step 2.

Please post results from both step 1 and step 3.