Glommer Map Spam

A map icon shows the last known position of an entity. If you leave the area it will remain there until you visit the place again (fog of war).

With things like grass and rocks that don't move it's assumed they are still there. When revisiting the place makes them disapper it's assumed someone else dug the grass/mined the rocks.

Glommer follows the flower, moves on its own and is unique. Thus it's assumed all appearances of the glommer icon on the map are from the same glommer.

 

So yes, it is caused by making the glommer sleep, leaving him in the area and then letting him catch up with you.
The same effect could be made with two people, one who will witness it and the other who will move the glommer in a coordinated fashion by having the glommer's flower in their inventory.

Changed Status to Known Issue