Spring under Octavia Seats get lose and drop

Guys, my two Skodas (Combi 2001 and L&K2002) has suffer the same issue. A spring under the front seats (each on each side) has come lose and drop on the carpet. Is a haft feet size spring.

The strange thing is that the seat work ok without the spring. They move forward and back ok. So I dont undertand what this spring do on the seat.

Have any of you have this same issue??? What is this spring do???

THX,

Isaac