Thanks for replying.
The location of the take over module could not be changed as all wire goes to that location. The strange thing is with two take over units, only one reports lost of supervision (once in few days) and another one just works fine. We already added an 2gig official repeater but still happening (less often than without repeater). From GC2 panel manual, we can adjust check in time to 12 hours / 24 hours (in this discussion you mention it ), but not for Edge, looks like I can only disable the supervision or enable it in Edge.
BTW, It will be highly appreciated if you could address above 1st and 2nd question.