MediaCache HTTP Origin fetching content

Using Wowza 4.7.3 (build 21227)

I'm streaming HLS content through Wowza, and while the streaming works well the origin server is being hit by Wowza with around 30reqs in one sec (206 partial requests), every few seconds having Content-Range: bytes 157474993-157483567 (8kb). Is this behavior normal?

I changed defaultBlockSize to 6M and restarted Wowza and for a while it went well (just a request every few seconds) but after one hour or so it goes back to something around 30req/second in bursts.