I used mostly Normal and Hard DCs for their level
How have you been handling environmental challenges, in general? Chase obstacles shouldn’t have DCs that are explicitly scaled to the party level; instead, they are tied to the obstacle’s level (which means the DCs might be implicitly scaled to the party level, if the challenges are on-level for the party).
I just ask because this is something I see a lot of GMs do that causes problems, they scale all DCs with the party, even for things that should have static DCs. And if I were free-wheeling an unprepared chase scene, I, personally, would be leaning on the Simple DCs table, not Leveled DCs.