renderPlotly creates lines between points when combined with ggmap

It's hard to say without a reprex (short for minimal reproducible example).

Right now the best way to install reprex is:

# install.packages("devtools")

If you've never heard of a reprex before, you might want to start by reading the help page. The reprex dos and don'ts are also useful.

For pointers specific to the community site, check out the reprex FAQ, linked to below.