I’m 99% sure that the test cases for the problem MFREQ in the current contest are faulty.
To be more precise, I think that the author’s and tester’s solutions will print elements that appear exactly k times consecutively in the array [L, R] for each query, whereas the description says to output -1, and print the element only if they appear more than k times.
I think this is the case because I wrote a simple brute force solution and it gets AC with >= but WA with >.
This is also why the problem has such a low accuracy and a relatively low amount of successful submissions.
EDIT: Description was fixed.