Special:Contributions/<username> should list contributions,with rollback and Twinkle vandalism reversion links suffixed to each one. Recently they've broken.
Links are now of the form:
https://en.wikipedia.org/wiki/2019_World_Aquatics_Championships&twinklerevert=norm
Note that the first URL param is delimited by a &, when it should be a ? As a result, broken link.
Rollback links look okay on Special:Contributions to me:
https://en.wikipedia.org/w/index.php?title=redacted&action=rollback&from=Krenair&token=redacted%2B%5C
Maybe it's just IPs?
I don't want to imply any blame to this (blameless) editor, but I've just manually reverted the ones who had been vandalising, so the actual problem links are gone now. But take a look at the top here.
Also I use Twinkle, which might be involved?
https://en.wikipedia.org/wiki/Special:Contributions/87.244.78.142
I get https://en.wikipedia.org/w/index.php?title=2019_World_Aquatics_Championships&action=rollback&from=87.244.78.142&token=redacted%2B%5C
I also have the Twinkle gadget enabled
Oh I've just noticed Twinkle's own blue rollback link to the right is the thing that's broken. MediaWiki's one is fine.
This will need to be reported to the gadget developers.