This summer we have had problems calling our summer house, which has a POTS line, using our Phone Power phone line from home. Calls would not go through or those on the other end could not hear us. It occurred mostly in the evening. During the day it seemed like the calls would go through fine.
Are the people at your summer home using cordless phones?
If so, is the location of the handset any different in the evening compared to the day?
For example, in the daytime picking up the call on a handset in the kitchen or den, near the base station for the cordless phone.
Whereas at night, picking up the call on a handset in the bedroom or on the patio, further away from the base station?