Full Items should be completed respecting the order by which the components/units were acquired instead of randomly combining them.
Lvl 1 unit has component 1 and was acquired 1st.
Lvl 1 unit has component 2 and was acquired 2nd.
Lvl 1 unit has component 3 ans was acquired last from the carousel.
In my game, when the unit was automatically upgraded to level 2 combining 3 level 1 units, the game also combined component 2 and 3 together into a full item (or 1 and 3, can't tell since 1 and 2 were identical), instead of combining component 1 and 2 together, effectively costing me the game.