After pasting a link I realized I could no longer scroll back up my document using k and had to gg to get off of the line.
Afterwards, I can move up and down freely until I go to the end, say, using $ on the last line. This then locks my cursor to the single line once again.
Please resubmit this bug report and make sure that: 1) you follow the bug report template, 2) you use the default theme (no css) and 3) there are no third-party plugins enabled (You can use the help vault for 2 and 3).