Collectible Card Game Headquarters

Describe the Bug:
1-Magus of the Arena I select which creature of opponent will fight.
2-A small bug which I can't think of a scenario that it makes any difference:
Magus of the Arena first selects target creature you control and then taps.not a bug

Which card did behave improperly ?
Magus of the Arena

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
ML3- Onslaught.v2

What exactly should be the correct behavior/interaction ?
1- Opponent chooses which of his creatures will fight mine.

Are any other cards possibly affected by this bug ?

Already rewritten.

(And aren't tapping (as part of paying costs) and target selection supposed to happen simultaneously?)

It seems it is one of those days for me that I see bugs everywhere and even basic stuff look they need investigation