Got this off the GW2 wiki page worked for me.
There is a currently a bug making you unable to pick up the hay to feed the animals, this makes the achievment impossible to complete. NOT IMPOSSIBLE: frustrating but not impossible. Do not do the witnesses that feed the turtle(cant anyway) and dont do the witness where you pay 3 gold. Do the instance twice. First time do the rest(8) of the witnesses. This will advance the story and give you 2 credits toward achievement. Now GET OUT of the story by logging off. Log back in and do the story instance again, doing the same 8 witnesses again. This will finish achieve and let you go on with the story. Do not go over to the second scream before you have done this else it will advance the story and wont let you get the additional witnesses. If you do accidentally get to close, just start the instance again.
Got this off the GW2 wiki page worked for me. There is a currently a bug making you unable to pick up the hay to feed the animals, this makes the achievment impossible to complete. NOT IMPOSSIBLE: frustrating but not impossible. Do not do the witnesses that feed the turtle(cant anyway) and dont do the witness where you pay 3 gold. Do the instance twice. First time do the rest(8) of the witnesses. This will advance the story and give you 2 credits toward achievement. Now GET OUT of the story by logging off. Log back in and do the story instance again, doing the same 8 witnesses again. This will finish achieve and let you go on with the story. Do not go over to the second scream before you have done this else it will advance the story and wont let you get the additional witnesses. If you do accidentally get to close, just start the instance again.
