Bug introduced in version 11.1.0 and fixed in version 11.2.0
The infinite limit
Assuming[a>0&&b>0, Limit[((1+a)*b*x)/Sqrt[1+(1+a)*b*x*((1+a)*b*x+Sqrt[1+(1+a)^2*b^2*x^2])], x->Infinity]]
gives the correct result
1/Sqrt on version 11.0.0 but gives the incorrect result
7/8 on version 11.1.0.
What exactly has changed and what are the pitfalls we need to be watching out for?