Help-Odd smell - not sulpher!

I am redoing a first floor bath. A plumber came to connect the shower and toilet. He also plumbed the vanity wall for a wall faucet - which is not connected yet. The vanity sink drain pipe is plugged with a cloth and plastic to block sewer gas - but the smell is not coming from this.
We have been able to use the shower and toilet for about a 10 days. A few days ago I noticed an odd but familiar smell. It is not typical sewer smell - I believe it is coming from the shower drain. It is almost chlorine like. Years ago, in a different house after months of constant cleaning and sniffing, I discovered it was coming from the shower drain. The shower was on the second floor, and someone told be that the drain pipes might not have been angled correctly. If I ran the water for a few minutes, the smell would go away for a few hours. This is the same smell.
Since this shower is on the first floor, I have access to the pipes from the basement. Instead of a pre-formed P-trap, the plumber created one from two peices of curved PVC to more easily navigate the floor joists. Could the extra width of this p-trap cause this? Again, it is not the same sewer gas smell that is evident from the unconnected vanitiy drain (if I were to remove the rag and plastic plug). I attached a photo of the p-trap with a pre-formed one held up to it for comparison.
And what can I do to stop it?

I'm suspect but would like to see how it is attached to the drain of the shower and the drain itself with any venting...

Can you post a pic from a different angle?

Attached are two more photos. It is a little difficult to see but again, in order to accomodate the floor joints, the drain exits through shower floor into two slighltly curved PVC peices that then go into the ersatz P-Trap, then back up to the left, rejoining the original copper drain pipe. It does look like the pipe slopes toward the P-trap where the photo is marked "connect to copper". I am not sure what you mean by "vents". We had a Fanteck ceiling fan installed with this redo, where previously we did not have a fan at all, but instead a heater/light. As for the shower base, we used a one-piece Redi-Tile shower pan - it can't leak, the drain part is molded into the pan itself. Thanks for your thoughts.

I'm seeing a trap that is a bit on the deep side...
Not much but a bit...
The pipe on the outlet side looks backpitched in the picture...
Is it?
There is no view if the vent...
Try shooting again from further away.

It is slightly pitched toward the p-trap. What do you mean by the "vent"? The new pvc pipe connects to the old copper pipe, which in turn, connects to another drain pipe that leads out to my septic tank. What should I take a picture of?
Also, everything you see in the pictures as white PVC, used to be copper. We cut out this section of copper only, and replaced it with PCV. Nothing else in the basement plumbing was changed.

Do you think the fact that the drain pipe tilts every so slightly (about 5 degreee angle)toward the p-trap could be causing the problem?

Yws but there can be other problems as well thats why I asked for a different picture.