Raising and lowering the primary weapon or sidearm while walking or running stops the character sometimes, makes him perform weird animation maneuvers that cannot be aborted and often feels clunky and/or not smooth.
One particular bug even locks the player in place and disables movement input. See issue #14759
Arma 3 infantry movement is a lot better than previous installments, but some areas needs still some polish.
Example 1, primary weapon raised, standing:
Start running forward and strafe right or left at the same time then lower weapon. Character starts sprinting for a short time then abruptly stops and continues with normal speed
Example 2, primary weapon raised, crouched:
Start running forward then lower weapon. Character raises the weapon, then lowers it, stops and then continues to run
Example 3, sidearm weapon raised, crouched/standing:
Start running, crouched or standing, lower weapon. Character stops, performs lowering weapon animation then start running again.
Example 4: primary weapon lowered, standing:
Start walking, press fire once. Character stops, raises weapon then continues to walk.