I assume you claim there are two animations for quickstep, and that the game ‘randomly’ picks one or the other, giving you no control over your dodge distance. By control mechanism, I assume you mean separate key bindings. Is this correct?
Could this be an issue with double dodges? Since you mention the Shift key, you likely use mouse and keyboard. Does the following video depict the two types (long, then short) of quickstep animation?
Due to a known bug, both of these (the double dodge, then the single dodge) can be triggered with a single press of the space bar each. You’ll perform a double dodge if you release the space bar within 180 to 230 ms of pressing it, and a single dodge otherwise; see here. This felt ‘random’ to many people.
If this is not it, could you please create a recording of the two distinct quickstep animations?