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: Multiblocks: Display only active blocks on the top of blocked user's Special:Contributions page / when editing a blocked user's user [talk] page.