If you click on a creature not in your main party to swap, and without clicking another creature's position, sell, or cancel buttons, and you buy a creature from shop that merges the creature 1 star higher, The “Sell/Cancel” buttons will be gone from where that creature used to be. Clicking anything else makes the creature “spawn” out of nowhere, which is a serious glitch as it also does not make the merged creature retain their star. In short, it takes up your space, and the max stars of said creature will be 2* in your party.

Glitch in work:

What it shows on screen.

What it shows I have on my party. Notice how the Golden Unicorn have both stars lowered by 1.

Steps to reproduce (that I know of):

1. Have a creature that can be merged one star higher on your main team, and the rest of the creatures on your waiting space. Make sure you only need one more 1* of that creature to merge up.
2. Have the same 1* creature available in shop to buy.
3. Click any of the creatures not in the waiting space.
4. Buy the creature from the shop.
5. You will notice the Sell/Cancel buttons on where the clicked creature used to be is missing. Click anywhere, it will “spawn” the creature.
6. On battle, you will see either the merged creature or the spawned creature with the glitch of being 1* lower than it should be.

Notes: haven't tested for if you click the creature already in your main party. Also haven't experimented it further as Arena takes a long time to play.

Thank you for the report. I'll try testing to see if this is a visual bug or if the companion is actually at a lower level in battle. The Bug Index has been updated to include this issue.