Use case is to display the products from the same category, which visitor is currently accessing
Criteria Definition used is : Most Viewed Item as Recommendations Key , with Content similarity type
When using content similarity with Most Viewed recommendation key , visitors recommended product might change on each refresh of the page.
This happens beacus the most viewed key of the visitor might change with each refresh of the page.
You should be using Content Similarity with the ‘current Item’ as recommendation criteria in place of Most Viewed key