How to Deal With High Return Rate Due to Amazon Fulfillment Problems?

I sell niche products in the US and Europe (UK/DE/FR/ES).

My return rate in the US for this year has been less than 1%. In Europe, the return rate is closer to 5%.

80% of my Europe returns are based on problems with Amazon fulfillment. Customers claim the FBA item never arrived. Customers order multiple items from me in the same order, but claim that only some arrived in the package. Customers order items shipped to Amazon lockers and simply don’t pick them up within 2 weeks, so they are refunded in full and I have to eat all the FBA costs and refund costs.

I actually had a German customer contact me, saying that Items A and B were ordered at the same time, but they only received item A. I instructed the customer to contact Amazon for a refund or replacement. The next email I received was a refund notification from Amazon for item A, the one the customer claimed to have received! Hours later, I received a second refund notification for item B, the item the customer claimed was missing!

If not for these FBA related problems, my actual return rate in Europe would be about what it is in the US, about 1%.

Here is what I see in my FBA return reports from the past couple weeks, and it doesn’t even take into account a recent string of refunds that all seem to be due to fulfillment related issues:

Besides raising prices, what are other sellers doing to deal with the problem of FBA issues resulting in an excessive amount of fulfillment related refunds, in which all the costs are being passed to the seller?

p.s. Don’t you just love how when the “Customer Return Reason” is a fulfillment related reason, it simply shows “Unknown Reason?” Amazon can’t even take responsibility for their mistakes enough to add a reason like “Delivery Problem” or “Service Issue”