Globetrotter - can't unlock

[Kenshiro]

Despite completing and visiting all arenas with both units, I can't get this unlocked.

And explanation as to why?

[KacQ]

I have the same problem :/

[topolskiego]

Same here, this is the only achievement I'm missing.

[TheBestOfSylw]

I have this same problem, can you fix it yet?