Why did my team score drop 60pts all of a sudden? Is this a bug?

Platform, device version and operating system:
Nintendo Switch, 13.0.9

Screenshot or image:

What you were expecting to happen, and what actually happened:
I had been playing the game almost everyday and my team score with the exact same troops had been steadily going up as I levelled up. I never changed up my squad and I got to a team score of around 7012. Then, earlier this month in September, my team score went down to around 6960. I’ve been grinding to get it back up and I’m just under 7000 now but I’m still been a few weeks. Never happened before so is this some kind of bug?

How often does this happen? When did it begin happening?
I’ve played this game for a few years now and this is the first time this has ever happened.

Steps to make it happen again
No repro steps as this has only happened once to me ever.

Is your hero on the team? If so, did you change the class your hero was using?

This could also be related to guild bonuses expiring. When an epic task is completed, it gives a stat boost to all guild members for 7 days.

Does your guild sometimes complete epic tasks?

Edited: stat bonuses are awarded by all tasks, not just epic tasks

Just in case you aren’t aware, a high team score isn’t a good thing, it’s a bad thing. The game scales down various rewards as your team score goes up.

I don’t know if this affects anything, but if you copied another player’s team who didn’t have as many class talents unlocked as you, even if you pasted into another slot, your main team’s selected class talents will also be affected (unless this has been fixed).