Hello, i think this is a bug and i already asked a judge who confirmed that this is a bug.
When Lose 1 turn is already on the field and i special summon a gemini from my deck (in this case red eyes black flare dragon), the dragons effect gets negated and goes into def, wich is incorrect because its a normal monster on the field.
Would appreciate a quick fix 🙂
The Judge should read the card.

Lose 1 Turn
Activate this card only if you currently control no Special Summoned monsters. During the turn a monster is Special Summoned, negate its effects. If an Effect Monster(s) is Special Summoned in Attack Position: Change it to Defense Position.

So you Special Summon a Gemini Monster. It's effects get negated by Lose 1 Turn, thus it is an Effect Monster so it will be changed to Defence Position.
you cant negate the effect when there is none
Skill Drain Vs Gemini
Normal Gemini monsters have their effects negated, and are treated as Effect Monsters. They do not gain their effects that are gained when Gemini Summoned. You cannot Gemini Summon such a monster.
Effect Gemini monsters have their effects negated. When "Skill Drain" is removed, the Gemini monster is still treated as an Effect Monster and regains its effect. 
Originally Posted by: Dortmunder 

you cant negate the effect when there is none

Gemini monsters are not normal monsters. They are effect monsters treated as normal monsters by an effect. If that effect is negated, they are effect monsters. Lose a turn's first effect is continuous, and negates the effect of any Special Summoned monster immediately when it hits the field, including Geminis. By the time the 2nd effect triggers, the Gemini is already negated, so it is not treated as a normal monster.