Sewer smell and sewer flies?

It probably is a hazard. make sure nothing is clogging the drain in your shower. You may have to get a snake and remove the clog. I had to hand dig a sewer line all the way to the septic tank only to find the homeowner who we rented from used a corrugated plastic pipe for the line and tree roots was blocking everything. I installed a clean out and 4 inch pvc. It was no fun because when I removed the clog every flowed out.