There are 3 bugs associated with the spear on the final boss encounter in Spires Of Ascension.
The first bug (spear not working on far left or far right), which was fixed last reset, can be seen here:
https://streamable.com/ng67ec
The 2nd bug is inherent in the targeting reticule system that is used in this encounter and a bunch of awful world quests. The targeting reticule will magnetically attach to the closest object in its path. On the spires fight, this is often the bubble that is cast by the friendly Kyrian, which is invisible to the person operating the spear. This will cause the spear to fail completely and just fall to the ground.
There is a video of this bug here:
https://www.youtube.com/watch?t=277&v=0Phzc0F5Mm4&feature=youtu.be&ab_channel=MichaelArmstrong
The third bug I believe to be latency related and the spear will just fail even though obviously hitting Devos. A video of this can be found here:
https://www.twitch.tv/mateuzotv/clip/PoliteSmilingSharkCopyThis
and here: https://www.youtube.com/watch?v=Kx7KkahqEj0&ab_channel=Gretel
Nothing has been done to address the 2nd two bugs on Devos which are still wrecking otherwise timed keys by wiping groups due to a buggy vehicle mechanic which has no place in serious play.