I've tested three "other" workouts in the last week on my new Steel HR, and though everything looks fine starting, during, and stopping the activity, after sync it is not displayed anywhere in the app. I have no problem with other categories of workout. I use "weightlifting" regularly and it's fine.
I note several other posters on the forum with the same problem, responding to threads like https://support.withings.com/hc/en-us/community/posts/360025219193-Workouts-not-logged- . This is clearly a bug... Do the app developers monitor this forum?