An error when trying to import/export themes appears. This happens on all October 458 versions. See screenshot below for more details.

Thanks for the report @drmzio. Fixed as of https://github.com/octobercms/october/commit/5723cd4b2ae1b216518da8da42ca78b3d0aef766.
Hi, how can i update to this fix?
I just did a fresh install of october and i am on build-number 458 with the exact same bug with no updated available :(
@cdreier set enableEdgeUpdates = true in config/cms.php and update to build 459.
@LukeTowers thanks a lot for that fast help!
@cdreier no problem!