It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

So this is the case, i unlocked the "jump over traps" challenge, and after trying it a few times with no success, it disappeared from my challenges list, I restarted the game and it came back, but the second time it also disappeared and now it doesn't get back when restarting.
I have also tried creating a new character, but the challenge is still missing and the marker to unlock it is now gone.
This question / problem has been solved by dr.schliemannimage
This may help but requires a bit of hex editing.
Post edited September 09, 2018 by dr.schliemann
dr.schliemann: This may help but requires a bit of hex editing.
Thank you very much for your answer, i'll try it as soon as i have the time, it doesn't seem that difficult.
Again, thanks for guiding me to that post