I tried several other things :
repeat the steps with blue rifleman : Bug
repeat the steps with red rifleman : bug
tried without removing gear (blue rifleman): no bug
tried without removing helmet + NVG : bug
tried without removing plate carrier : no bug
tried without removing weapons : no bug
tried with a diver (remove the breather + weapons : no bug
tried without pressing shift : no bug
tried the step by step on several location : bug
tried the step by step without diving : bug

I deduce the bug come from the combination of : no plate carrier, no weapons and holding shift. (+ you must not be a diver)