Steps to reproduce

1. Import mc_addon_test.mcaddon and apply it to a new world set to peaceful, survival, cheats on.
2. /summon fur:barco_1

Expected result

The fur:barco_1 (colored cube) summons 1 group of 3 fur:barco_2 mobs (black cubes) and stops.

Observed result

The fur:barco_1 (colored cobe) repeatedly summons groups of 3 fur:barco_2 mobs.

Note

If you change the mob it summons to "minecraft:sheep" or just "sheep" it will only summon 1 group of 3 and stop. This suggests that during the check against summon_cap value the game is assuming or interpolating the "minecraft:" namespace into the name of the summoned mob.