This is a copy and paste from a Ticket I wrote to Support who referred me to create a post here .
Ticket Follows:
Different maps will give different DPS and Damage readings on weapons. This is understandable when looking at Space weaponry when on a Ground map, or vice versa. However, when I am on a Ground map that allows combat (New Romulus, Delta Battlezone, Ground Episodes, etc.) something odd happens.
When I have an unequipped weapon in my inventory, it will show one set of numbers, but when I equip that weapon, it will drop significantly in effectiveness, despite my character being overwhelmingly geared towards using that particular weapon.
For instance: I have a Mark 14 Romulan Plasma Compression Pistol. When I look at it in my inventory while it is unequipped, it says it deals 225 DPS. When I equip it on my character, it drops to around 196 DPS. This character is fully decked out with a kit that provides a bonus to weapons, as well as plasma damage. The character also has all ground skill points allocated towards high ground weapon damage. Furthermore, the traits she has equipped for ground use are mainly damage increasing traits.
This mainly seems to occur on combat maps only. On most other maps, this "debuff" will not usually take effect (though, it sometimes does). The captain has no injuries, so that is not where the debuff lies.