WOW! That's an improvement.
The big hike in latency, which looks rather like 8ms, is the typical increase when interleaving is turned on on FTTC. Looking at your line prior to that, it seems likely.
The first step of interleaving tends to cost about 10Mbps downstream sync.
One of two things should happen at an indeterminate time in the future. Either it will revert to Fast Path or G.INP will be implemented n your line. In both instances the latency will drop by 8ms and the 10Mbps regained. Though latency can change independently of this as well, probably depending on the routing each time you connect a PPPoE session.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
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