Hi,
After dealing with the same issue for 2 hours I figured it's a Bug in Ableton 11.
I dropped a simpler in the drum rack and set it to classic, it played the sample as it should as long as the note is held.
Setting another drum pad to classic (with the default simpler) still lets the sample play until end.
Solution: set it to classic then change voices (I know, completely unrelated setting) to whatever number, then it will work.
After you can change voices back again, it just needs to be changed for the simpler to understand in which mode it is.
I reported the bug to Ableton.
Hope this helps.