The description says it all.
Running on Chrome on Linux Mint.
Push/Pull doesn’t work on edges. It works on faces. Have edges selected makes no sense in terms of the operation of Push/Pull.
Could be a graphics driver problem. Are you up-to-date?
By “drop” do you mean they cease to be selected? If so, as @DaveR pointed out, this would be expected behavior. Push/Pull only works on surfaces, do selected lines would be discarded when starting Push/Pull.