The positioning of the mouse cursor over the rope end in order to pull the rope appears to be much more critical in Firefox than in Chromium/Chrome.
As mentioned, the mouse cursor must change into a double-pointed vertical arrow, to allow rope pulling, so the shape change identifies the right spot.
Nice of everyone to downvote my report though, as if I was just making things up in here to troll.
The positioning of the mouse cursor over the rope end in order to pull the rope appears to be much more critical in Firefox than in Chromium/Chrome.
As mentioned, the mouse cursor must change into a double-pointed vertical arrow, to allow rope pulling, so the shape change identifies the right spot.