Apparently after X minutes or whatever, backfilling simply doesn’t work.
I had about 8 games today.
First one ended with us playing the last 6min of the game as 3vs3. Not a single player was added to the game from the start. (someone got afk kicked right after start or so)
2 games I joined as backfill, within first two minutes since the map started. Both games went well.
3 games didn’t have backfilling once we were about over 6min into the game. With 1 player down, those games ended quickly.
And backfilling didn’t happen for any of the games once we were on the last objective and there was less than 4 min left.
This happened in EU, within ~18-22 GMT+3
According to steam, DB had over 5k players during this time.