I'm with BT on profile 17a . I set 30a years ago in case that ever happened but the router will only ever connect on the highest available , that being 17a.
Out of curiosity, I changed mine to match yours, went from 33 to 37 download.
Probably just the router settling in, or it did make a difference, who knows 😂
Probably coincidence but time of day reconnecting can change things a bit.
Good point @TimCurtis
I'm going to monitor over the next 2 weeks.
I've got a new microfilter coming today, to test if the BT one does infact change rates.
Thanks for all your help.