Hello Michael,
Thanks a lot for your query and we are so sorry about the trouble this must have caused.
Sorry for the late reply. Seems your post got stuck in the spam queue due to use of multiple links in your post.
Even though the pages might appear twice in your analytics, they are already redirected correctly to the slashed version. Moreover, they both have a proper canonical tag so there is no reason for duplicate content issues:

There was a huge Google update recently that might be the reason for a drop in rankings:
https://twitter.com/Kevin_Indig/status/1196504709432934400
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.
Thanks, very much appreciated,
Michael
Hello,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/?rate=5#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.