IP ID addresses change to an other in some terminals

Hello,

We have noted in the extensions list of the Forivoice monitor that some extensions IP Addresses changed from 192.168.24.x to 45.143.221.14 (four or five, all with the same IP Address). Reviewing the terminal, doesn't change IP, only in the monitor and these extensions could not be reached by others, However, terminal is capable to call to any other extension.

Has anybody an idea of this trouble?