I am doing this event daily with several characters on my account, and at some point in the day I find it bugged, 100% guaranteed. There have been numerous threads about this, some with very extensive investigations as to what causes these bugs but so far, no fix. Here is a very old explanation about how the event bugs, not sure if some fixes have been applied since then, but it still bugs solidly every day, despite any fixes. https://www.reddit.com/r/Guildwars2/comments/2ngcjb/tips_on_how_to_prevent_ogre_wars_foulbear_kraal/
In my own current experience, when it is bugged, there is a possibility of 2 different situations:
1) In Hunter's Gorge (the area where the war takes place) you will find an invincable Legionaire Slashclaw fighting of Ogres that attack him endlessly, forever. You will also find Vanguard Scout Finley, 2 Ebon Vanguard Warriors and 1 Ebon Vanguard Soldier nearby, standing around, doing nothing. The Event text sais: " Ogre Wars. Charr and Vanguard forces are assaulting Foulbear Kraal and its leaders"
2) Same situation, exept no Legionaire Slashclaw this time, just Finley and his buddies. I think it is the same Event text, will double check. COuld be that is sais something like " Vanguard forces are assaulting......" since the charr Slashclaw is not present, representing the Char side of the attack.
In any case, at some point, one of these assault events are not finished I think, bugging the event? Is there a way to check if this happens when nobody kills the Foulbear Weapon Master, or maybe the Foulbear Master Trainer after that?
It is a pity since this is a popular event that still attracts a lot of people due to the chance on a high prized item(Sam). It is also several Dynamic Events in quick succession which means loot, XP and a nice way to level up lower characters too. Anet is big on keeping old content(and zones) in the loop and this event makes Field of Ruin one of the go to destinations of the game.
I hope Anet will find the time to implement some sort of fix. Maybe just reset the whole sequence every hour if certain bugged conditions are met: like Slashclaw and/or Scout Finley being in the same location for an hour. That would already solve 99% of bugged events, I think.
NB: Often there are people afk-ing for a while in Hunter's Gorge, waiting for the event. I feel that this is part of the reason why the zone has a hard time resetting itself when it is bugged(assuming that a zone restarts fresh when it has been completely abandoned first and then someone enters it. Not even sure if it works this way). Very seldomly have I returned after half a day to find the zone OK again. More often the zone stays bugged untill server reset at night (or whenever that takes place)