Neighbours on FS switch shows only switch 1 in a stack

FS Switch S3410, in a stack of 3 elements, shows only the neighbours connected to the fist element of the stack, even if there are several other devices.

I've made a check using Mib Browser, and the result of the SNMP walk is correct and shows all the elements.

Attached the screenshot of MibBrowser table of the LLDP MIB, the discovery with "-dddd" option, and screenshot of the elements shown on the web interface.