AFAIK substrings ({%pattern} string) has never worked since release (including testimonies from other developers). This is incredibly frustrating to work with and borderline makes the translator portal useless because it scrapes hundreds of duplicate strings where otherwise the substring feature should have deduplicated it.
Setting autolocalize to false on the problematic textlabels doesn’t inhibit the strings from being auto-captured (separate bug: Auto-Capture doesn't respect AutoLocalize). It seems to happen when the pattern contains numbers, say you have the string {Player_Name} has joined!" and a player named “BloxyCola21” joins the experience then the machine translated string returns BloxyCola{number1} has joined!.
Expected Behaviour:
I expect that BloxyCola21 should match {Player_Name} and not be fragmented by a separate number pattern so that it doesn’t create another entry in the LocalizationTable