I have much the same issue ongoing at the moment. If you google "PPP LCP Send Termination Request [User request]" you'll find dozens of instances going back to about 2014 involving the HH5/Plus Net Home Hub in the BT Community and PlusNet forums.
very interesting. so it looks like I may have to obtain a different router like a TPlink one
regards,
Woody (chuntering along in his own inimitable style, using 100 words when 10 would do)
Woody (chuntering along in his own inimitable style, using 100 words when 10 would do)