I keep seeing this (mentioned in the other thread). Land lines are oversubscribed just like cell lines. Land lines are lower profit than cell lines and therefore get less focus. Land lines have not been reliable in years.

My parents live rural, their land line goes down every time the sun does and it takes a month for the phone company to fix it.
In the city our land line would go down all the time. old infrastructure, companies accidentally cutting cables, trees not being pruned, etc.

The backbone between cell tower to cell tower and between local exchange and local exchange is the most reliable. The last mile to your house is the least.