Thanks for the help, turns out that while loop was the issue. I replaced it with a for loop instead and it solved the problem. No idea why I didn't use a for loop in the first place instead of beating my brain trying to figure out why my while loop wouldn't be exiting correctly.

I did not analyze your code deeply, but after a quick test with it, I fear your while loop on line 20 sometimes never ends (on some tests it reaches over 1000 iterations).

Tests are ok in Python, though they could be enhanced to return an explicit message rather than a raw error. The problem comes from your solution, that does not match the expected result, so some verification fails.

5 is not a peak, the next value is greater.

shouldn't potential a peak value be greater than last and first el in order to actually be a peak?

No, being a peak (or local maxima) depends on the surrounding values.

ok. Thank you
But what about 5 than?

Also, if last and first elt-s should not be considered as peaks which is clear, shouldn't potential a peak value be greater than last and first el in order to actually be a peak?

Sorry for the late reply, your code is wrong, it's giving false positives on things that aren't plateaus. Print the input and you'll see it.

The first and last elements of the array will not be considered as peaks (in the context of a mathematical function, we don't know what is after and before and therefore, we don't know if it is a peak or not).

3 is the only peak there. Use Question label next time.