I am not sure if the issue is only when a power does 1d6 damage, but there have been many times that instead of generating the power with 1d6, it generates it with 1d6+6. I can likely dig up a monster that does this if unable to find the issue.
If you can find2 or 3 examples, I will take a look at what is making it do that.
Here is one monster that causes it. Instead of 1d6 for Great Position it has 1d6+6. The stat card looks fine:
Goblin Warrior (level 4) Level 4 Skirmisher
Small natural humanoid XP 175
Initiative +6 Senses Perception +2; low-light vision
HP 54; Bloodied 27
AC 20; Fortitude 16, Reflex 18, Will 15
Speed 6; see also mobile ranged attack and goblin tactics
m Spear (standard; at-will) ✦ Weapon
+9 vs. AC; 1d8 + 3 damage.
R Javelin (standard; at-will) ✦ Weapon
Ranged 10/20; +9 vs. AC; 1d6 + 3 damage.
R Mobile Ranged Attack (standard; at-will)
The goblin warrior can move up to half its speed; at any point
during that movement, it makes one ranged attack without
provoking an opportunity attack.
If, on its turn, the goblin warrior ends its move at least 4 squares
away from its starting point, it deals an extra 1d6 damage on its
ranged attacks until the start of its next turn.
Goblin Tactics (immediate reaction, when missed by a melee
The goblin shifts 1 square.
Alignment Evil Languages Common, Goblin
Skills Stealth +11, Thievery +11
Str 14 (+3) Dex 17 (+4) Wis 12 (+2)
Con 13 (+2) Int 8 (+0) Cha 8 (+0)
Equipment leather armor, spear, 5 javelins in sheaf
Here is just the power line for one that caused it just in a game recently. Instead of rolling 2d8, the converted power rolled 2d8+8. Again, the stat card was fine; only the DN power listing.
A Thuranni assassin deals 2d8 extra damage on attacks against
any creature granting combat advantage to it.