Line faults can cause all kinds of erratic things.
I've experienced similar ringing with a line fault.
High-resistance joints often affect ringing as the ring voltage is intermittent.
Good luck getting it fixed mate.... took me over a month and 4 tech visits for Telstra to finally allocate a different pair in the street.
Useless Manila faults people kept telling me the line tested OK, even though they said they could hear the crackle on the line.
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