[Yashatari]

This first one me and my team mate are on the same tile, I use charge but no movement boost.
http://prntscr.com/im62c5
This second one me and my team mate are on seperate tiles, Movement increase activates.
http://prntscr.com/im62n5

Yes, I'm 100% sure i used charge in the first picture, I used it twice infact.

[Neus]

How are you and your teammate on the same tile?

[Fern]

and this, is to go... even further beyond! AAAAAAAAAAAAAAAAAAAAAAA.

On a more serious note, I feel the need to mention that whenever the 'spawning on top of each other' happens, some buffs seem to go towards the person... that is on top... apparently.

In the screenshot presented, my Shaitan duelist is under a Redtail mage. We were testing things when it happened and it turned out that buffs such as Sharpen and Charge would go towards the Redtail, when -I- used them.

We can't reliably reproduce the fusion bug because it happens randomly. Or so it seems. The tl;dr is that you spawn on top of your ally, and hilarity ensues.

So I'll take a wild guess and say that's what happened for our fellow when using Charge.

EDIT: I forgot to mention that the most common situation where I've seen this happen, involves a bush blocking one of the spawns.

I also forgot to mention that there was a bunch of invisible, dense tiles in that battle too. So that might've been it.

[Shujin]

Also spawning on each other happens when you have a bunch of NPC mobs with you in battles with a full team, that can cause you to spawn on top of each other. Mostly in Spatial dungeons I think, but not exclusively.

[Neus]

Well, the game should try to unstack you now when it occurs.