Over the years, much confusion has occurred with the application of racial ability score adjustments on PotM, so allow me to attempt to clear up some confusing aspects if I may.
There should not be any circumstance where you are only receiving a "+1" to an ability score from a racial adjustment. These adjustments always come in even numbers. It is more likely a bug if what you are seeing is correct. Its possible that the script may have become wrong and just needs to be corrected. If its true even after accounting for the following then I would report it as a bug and see if it can be replicated by others.
But first, there are a couple of things you should be aware of when playing a subrace. The ability scores of a subrace are applied on top of an ability score array that has already been adjusted for the "standard/vanilla" base race. In this instance, Potm is modifying an ALREADY modified elf. For this example, the race you are modifying is the base elf from the player's handbook. The base elf from the player's handbook/srd is the "High Elf" of Greyhawk or the "Moon Elf" from Forgotten Realms. If were playing either of those two subraces you would see no further adjustment by Potm.
So before the scripts modify your ability scores on Prisoners of the Mist as an elf, you have already received the standard ability score adjustments:
- +2 DEX, -2 CON
Any adjustments by the subrace need to take those preset adjustments into account. So for example, if the race has no penalty to constitution then the script applies an arbitrary +2 CON to negate the penalty that your character is not supposed to have. The same is true of bonuses too.
And lastly, there are two subraces of wood elves. Sounds like you are trying to play one from Abeir-Toril.
There is a subrace of elves known as "wood elves" in both the Greyhawk (Oerth) and Forgotten Realms (Abeir-Toril) settings.
- The wood elves of Oerth have: +2 Strength, -2 Intelligence. In their setting they are also known as sylvan elves.
- The wood elves of Faerun have: +2 Strength, +2 Dexterity, –2 Constitution, –2 Intelligence, –2 Charisma.
In their setting they are also known copper elves due to their skin tones, or "Or-tel-quessir" in Elvish.
What should happen when you select a Torillian Wood Elf is that Potm modifies your ability scores thusly:
+2 STR, -2 INT, and -2 CHA. The dexterity and constitution scores were already modified by the base elf adjustments.
I hope this helps clear up your confusion. Sorry you are frustrated.