At the maximum detection distance (8 blocks for skulk sensors, 16 blocks for calibrated skulk sensors), skulk sensors don't always detect the walk/jump/footstep trigger.

Here's a link to a .gif demonstrating the issue: https://drive.google.com/file/d/1KZAz9wSjIF8Ha26COriBDvySvBA_Uusu/view?usp=sharing

Actual behavior: It is possible to walk on the block 8 blocks away (or 16 for calibrated) from a skulk sensor without it sensing the trigger.  This seems to happen when the player is walking on a route that takes them over that 8th block.  (I.e., if you just shuffle around on that 8th block without moving anywhere else, the sensor will always eventually detect you.)  This is particularly evident if you have a line of sensors that are 8 blocks away from the path the player is walking.  Some of the sensors will trigger, and others will not. 

Expected behavior: Any time the player walks on a block within the skulk sensor's detection range, even if that block is the maximum detection distance away, the sensor should always trigger unless it has already just been triggered or is otherwise experiencing a cooldown.

Anecdotal note: Strange behavior at maximum detection distance may exist for other trigger types too, but I didn't test them all comprehensively (e.g., dropped items seemed unreliable to detect at max distance as well.)  By contrast, placing/breaking blocks at the maximum detection distance seemed to work with 100% reliability.