Wrong extension's state


I’ve got an Asterisk 1.4, some Audiocodes MP-124 (FXS ports), some Audiocodes MP-118 (FXO ports) and two Linksys SPA 962 wiith Spa 932 consoles installed in a company.

Whenever a call from the PSTN is answered by a member of the company who presses the “Flash” key on his analog phone, connected to an MP-124, the consoles automatically show a change of this extension’s state to “idle”, while it is actually Off-Hook and communicating with another extension to which a transfer is about to be done.
Many times the telephone operators on the consoles, as soon as they see the first extension “idle” (Asterisk’s CLI also shows it “idle”), try to send some other call to it and immediately get a busy tone.

Is there a bug anywhere? Is this a normal behaviour of the system? Is there any way to make Asterisk and/or the other equipment detect the right state of the extension, so that it is shown properly on the consoles?

Thanks a lot!