Posted this 2 months or so ago (now 3) but no one bothered and its still in the game.
Sightstone is unusable under very specific conditions.
To replicate:
Once you upgrade to a Ruby Sightstone upon using the UNDO feature your old regular Sightstone becomes completely unusable.
RiotRiot Afic5 votesWe are currently aware of this issue. Hopefully we will have a fix soon, but this is one of those pesky problems that would take a substantial amount of work to address (the thing that causes this issue prevents other, more serious bugs I believe) and the although this can be frustrating to have happen, there are other more serious bugs that are higher impact.
In the future if you can tag issues like this with [GAMEPLAY] in the title and follow the guildelines here I will be able to sort through bugs and get work towards getting them resolved faster.
Jesus is Savior1 votescan't you add an EXCEPTION for sightstone specifically?
Decrit5 votes.... if programming was this easy...
Jesus is Savior2 votes.....it really is?
Do you even program bro?
You would basically take the old code for the undo button, and do this:
if(item == sightstone) { <insert new exception code here> else { <insert old code here> }
Decrit2 votesFirst of all, calm down.
Every thing is made of functions, and functions into functions. If you reread the red post you can see that the main problem lies in this interwining of functions: if they do something to the undo function, posing that it' s only a single function for example' s sake, they need to tuch all the other ramificated functions, that by their own prevent even worse bugs. Exceptions like you say might be done, probably, but with very and very high costs in performance and chaos in the code, so that it' s a move that needs to be done only for critical, game breaking bugs. Now i don' t know how and how much is interwined the undo function, but i guess neither you do. And if a professional that works right on the project tells Riot Afic of this situation in this way i don' t really think how you can even be barely more right than him.
If you just want to sit behind your screen and say that at Riot are just lazy, then you are welcome to do so but don' t expect somebody to follow.
Jesus is Savior1 votesPretty sure the "more serious bug" that is being prevented is "using the undo button to refresh active items or GA by selling them and undoing it".
As a programmer and a gamer who has seen several game bugs, without knowing anything else about the code, that would be my first guess.
And I'm not just sitting behind my screen and saying that Riot is lazy. They have ADMITTED TO IT.
http://forums.na.leagueoflegends.com/board/showthread.php?p=50058519#50058519
"Sorry guys, I know this is a game-breaking Warwick bug that we have known about for over a month, but I just forgot to follow-up with the people who would fix it cuz I was busy and don't know how to manage my time on the job"
Decrit1 votesThat is just a sensitive way to put things. Plus, if you read again it says "follow-up with the people who would fix it cuz I was busy and don't know how to manage my time on the job", thing that makes me thing that they are all but slaking.
Jesus is Savior1 votesSubstitute "busy" for "browsing cat pictures on the internet".
Substitute "not knowing how to manage time on the job" for "I forgot to put a thing in my calendar to popup and remind me to stop browsing cat pictures on the internet"
No, but really, even if he is doing his job "properly" and not "wasting" time, you need to know how to use a calendar, set reminders, MAKE STICKY NOTES, ANYTHING, in a corporate setting. No one's going to hold your hand and make sure you're being efficient with your time.
Aina1 votesThis. 
Kobold1 votesyes
If you go >
then undo to make it back into then it loses all functionality.
0 Zone1 votesall you have to do is move the sightstone to a different item slot.
Wullf1 votesI just ran into this bug yesterday. I almost shat my pants when we where fighting near baron and I could not get any vision as my sightstone was disabled. Luckily I yellow pinged my team the hell of of there.