Hello Rich
1- Try the usual test of shining a torch at angles in case you can spot any Fungus or debris..etc.
Which you seems you already did?
2- Try shining a Black light (preferably long wave as Short wave is rather harmful to the eyes) to reveal any fungus or bacteria or maybe glue separation.....etc.
3- Take the lens out and place wide open with no caps in a well tight plastic container with an open small jar filled with Sodium bicarbonate. Keep the container closed for few days and check for smell and renew the Bicarb.
This will get rid of the smell and do the same in a different container for the paper work, strap, case...etc.
4- Last resort, send back to Solms for a CLA.
Whatever you do, keep the lens and all paper, case....etc VERY SEPARATE from your other lenses.
In the mean time, inform the seller of the situation and that you are considering sending the lens back pending your tests.
Good Luck.
N.B. Please be very careful when you use Black Light. I take no responsibility for this procedure and is entirely at your own risk.