Quests at the same place

I don't know if it can be considered as a bug but a few hours ago, after I finished my iron smelter upgrade at level 10, I received a new quest named "Ambush" in which I'm told to find the quest sign on the map. I didn't start that quest at once, and (let's say) half an hour later I already had two other quests:
1. Defend a region
2. Attack a region
When I went to the map to make my first quest, I noticed that only two signs of quests were put on the map, the "Defend" quest on region 38 and the "Attack" quest on region 41. No trace of the "Ambush" quest... I looked well in every corner of the map... no sign anywhere.
It's only when I finished my second quest (attack) that I saw the Ambush quest sign that was exactly at the same place than the previous quest on region 41.

Is it a bug or is it that the signs are given randomly... but one quest sign hid/covered the other.

Exactly the same right now!

Two quests "attack a region" and only one sign on the map at region 30.

The two quests are: 1 hard and 1 normal. On the map only the sign of the "hard" one.

I do it, finish it victorious, go to the quest list to claim my price: the completed quest is the "normal" one! (skull on green), which is now totally weird!

After a quick healing I return to the map, the sign is still on region 30 for a "hard" quest.

I do it, finish it victorious and go back to claim my price: the completed quest is indeed the hard one (skull on yellow).