Dynamic search campaign spend issues

Hi,

We have been running a Dynamic search campaign for a about 5-6 years now. Since mid last year, on some days we've been noticing some weird spend patterns.

Ex: Dynamic campaign doesn't spend during the first half of the day but spend starts to spike during second half (around 12-2pm Perth, WA time). We are based in Perth, Western Australia and the search campaigns run all around Australia.

FYI: This hasn't been the case before and it was always spending pretty close to a "half circle" pattern through out the day. Has anyone running Dynamic search campaigns have experienced this lately? Any idea on why this could be happening and how we could get this possibly fixed?

Thanks