See https://test.wikipedia.org/wiki/Special:Contributions/255.255.255.255
# I have test-blocked `255.255.255.255` along with `255.255.255.254/31`, so the box says `This IP address is currently blocked 2 times` (which is correct).
# Clicking `View block list` takes you to https://test.wikipedia.org/w/index.php?title=Special:BlockList&wpTarget=255.255.255.254%2F31 (where `wpTarget` is `255.255.255.254/31`)
# Notice that the block for `255.255.255.255` isn't included in the list, despite the fact that the page is linked from the contributions page for `255.255.255.255`.
# However, if you visit https://test.wikipedia.org/wiki/Special:BlockList?wpTarget=255.255.255.255, both blocks are shown.
So the fix would be to use `255.255.255.255` as `wpTarget` instead of `255.255.255.254/31`. I've confirmed that this is a long-standing issue that predates {T393902}.