Marsh map (random encounter) has a visual artefact (floating tile)

It was actually the first time I see this March map, that has a little wood cabin.  Random encounter with bunch of goblins. 

Game version : beta patch 1.2.14 / PC Windows 10 Pro /
WHERE : traveling near (towards) the Volcano area (I am heading to the sidequest in the Lava Forest after). 

Anyway, see picture :

nb : speaking of... as a party level 11, I feel I should not get 600 XP from killing 6 or so Goblins.