I am about to file an appeal due to the windfall clause. I worked in Switzerland over a 10 year period and receive a small AVS amount from them. When I filed for retirement (66) in February my benefit was lowered by $411 dollars. Here’s the deal. I asked for an explanation and was sent only a faded form letter. I am filing the appeal to see the actual calculations used based on all of the information I provided. I want to make sure the places I worked for in CH paid properly and that my ex’s income was included. Does that sound like reasonable grounds for an appeal? If I were rich and made much more every year than a social worker, this would not be an issue. So much for justice.
I can't tell from your limited description whether or not you have the basis for a successful appeal. The Windfall Elimination Provision (WEP) only affects Social Security benefits payable based on your own earnings history, though, so your ex's income would almost certainly be irrelevant (https://www.ssa.gov/pubs/EN-05-10045.pdf).
There is a WEP guarantee provision that limits the amount of reduction caused by WEP to no more than basically one-half of the amount of any pensions you receive that are based on your earnings that weren't subject to U.S. Social Security taxes. You say that your pension from Switzerland is small, so if the WEP reduction applied to your Social Security benefit is more than half of that amount then filing an appeal certainly sounds reasonable.