I have lost Russian Post packages again

This April, I have lost two packages which shipped to destination country Russia. I am one of the seller from AliExpress. There is no proof to show me where my items were stuck or they may be just disappeared. One buyer bought it in the early March, another is in Mid March. Now they all claim that they did not get their item. I am very frustrated as they were all sent through unregistered mail, now they cannot be tracked and found.

Usually, I will recommend my buyers and friends to go to TrackingMore and track their packages as it supports 410 couriers which apparently can meet most of people's needs. This time, I want to lower the cost of my item so that I can sold more products and earn more money, you know, to do so can benefit both me and my buyers as they can pay less fee to get a same product. So I chose a cheaper shipping way which turns out to be wrong.

If I chose to ship parcels via registered or international signed for services, then my customers and I can track our Russian Post packages and maybe we could not lost our packages. Maybe, I should avoid this unregistered shipping method or try shipping goods through other more reliable couriers, even a freight forwarding company.