This may be because you are inflicting overkill damage. Overkill damage means the enemy was already defeated by a fellow clubmate while you were in battle, so some of your damage was inflicted after the enemy was defeated.
Overkill damage on each stage is not counted towards the next stage.
For example:
- Players A and B both enter the raid at the same time while Glut has 20k health remaining.
- Player A manages to defeat Glut, and proceed on to Flotsam and Jetsam's stage and deals 10k damage to Flotsam before losing all their units. They see their new progress when they leave the battle, and see that the Raid is now on the Flotsam and Jetsam stage.
- Player B only deals 10k dmg to Glut. When they leave, they see that the club overall is now on the Flotsam and Jetsam stage. The 10k dmg dealt by Player B has effectively done nothing to contribute to the club's overall progress. However, on the internal club leaderboard, this DMG is still recorded.
Special Note: Since Flotsam and Jetsam are separate units, this also applies to them. If clubmembers have already defeated Flotsam in another instance, any damage done to Flotsam by clubmembers still in battle will effectively not count towards overall progress.