I noticed this during the WT study on Sunday.
1 Cor 15:23: "But each one in his own proper order: Christ the firstfruits, afterward those who belong to the Christ during his presence."
The Greek word for presence is "parousia", which needs no explanation here as to how WTBTS views this word versus the rest of the world.
What I noticed was the striking contradiction made just a few verses later.
1 Cor 15:51,52: "Look! I tell you a sacred secret: We will not all fall asleep in death, but we will all be changed, 52 in a moment, in the blink of an eye, during the last trumpet. For the trumpet will sound, and the dead will be raised up incorruptible, and we will be changed."
Verse 23, in the NWT, infers a gradual resurrection while verse 52 infers a quick and abrupt resurrection.
Comparing this with 1 Thess 4:16, we find agreement with 1 Cor 15:52: "because the Lord himself will descend from heaven with a commanding call, with an archangel’s voice and with God’s trumpet, and those who are dead in union with Christ will rise first."
My conclusion is that 1 Cor 15:23 is completely inappropriately translated by WTBTS. It should read, as nearly every other translation does: "when he comes" or "at his coming" or "when he arrives" or something similar.