Teeth sensitivity while chewing.

Is it normal to experience some sensitivity while chewing for up to 72 hours after changing trays? I’m on a 7-day change schedule and currently on tray 4 out of 20. The soreness pretty much stopped after tray 2. Now when I switch trays, nothing really feels different other than the trays being nice and clean, but I do notice some sensitivity while eating for the first couple of days. By days 4–7, it feels like nothing is happening, the sensitivity goes away and I almost forget I’m even wearing them.

Is that normal, or could it mean the treatment isn’t working as expected?