Fluttering Red Intercom light = auto redial is in use, or system is in night mode (at station 10 or 12, depending on the system setup)

Winking Red Intercom light = an LCD message is set on your telephone for others to recieve when calling.

On the other hand, the HOLD button flashing red indicates there is a message to pick up. This could be from a voice mail system, or can be sent from another phone. In your case, station 7. Who (or what) is station 7? From what you are describing in the body of the question, I'm wondering if the hold button lamp is the one flashing, not the intercom button lamp.

A fluttering red hold button lamp inditates automatic station relocation has been set.

Which lamp is flashing? Intercom or Hold?

It would be helpful for you to tell us what system you have and the type of phones as well.

The man who sets out to carry a cat by its tail learns something that will always be useful and which never will grow dim or doubtful. - Mark Twain