Used Summon Sorcery in 2 seperate battles in The Barrens (1) and the monsters are there as random objects on the map, but not centered on a tile (if that makes sense.)
Edit: This isn’t where I fought the battles where I used Summon Sorcery, this is after exploring and encountering this bug much later.
0.0.6 on Windows
PS: had a similar bug with monsters staying on minimap, but I haven’t been paying close attention when or why it happens. I think it was near God shrines.