Fuelweaver with thurible still roots (not consistenly, not sure why)

I am not quite sure why that happened, but FW managed to root me in this place with thurible down (it had a lot of charge left in it)
I can't quite test it yet, might be related to me shift dropping the thurible some time before attack (i did not drop it on attack im pretty certain) or FW blocking the vision of it for me? (i also got rooted on the other side of gateway, but thurible range is not that big anyway) Or maybe he started casting when i was a far and it got me when i got close?
I'll test it again later if i won't forget, but maybe someone knows what happened
Maybe im still too far from it? My bad if it is then, wiki says that it has 1.5 tiles, which should be bigger then the range here