When I ran the mission 'Fluid Dynamics' from the Borg Advance arc, the rewards listed were Very Rare Mark XI Antiproton weapons.
After completing the mission and accepting rewards, though, they are Uncommon Mark VIII Phaser weapons.
Even aside from the damage type change, Uncommon Mark VIII seems like the wrong reward for level 65.
https://cdn.discordapp.com/attachments/213368667570700288/1205257303373389876/image.png
Comments
The level at which you picked up the mission dictates the MK level of the reward. Additionally, when you're below level 40 (when you must have picked up the mission), the game will award Phasers, not Antiproton weapons.
If you look at the mission rewards now that you're level 65, you will see it rewards Antiproton weapons.
Just to further illustrate, here's my level 33 character showing Mk VIII phaser rewards:
Thanks. I guess that must be it since I ran the mission again and got the proper reward choices.
I did pick up the mission originally back in December. That winter event must have been great for leveling.