When translating Miosis from English to Swedish, the infobox is added into the translation with empty parameters:
In this case, the infobox is based on the template "Infobox medical condition (new)" which exists in both English and Swedish and it is connected through Wikidata. In this case, the Swedish version lacks templateData information (which prevents CX from completing the mapping), but the parameters used in the template are exactly the same since the template was ported into Swedish from English. In this particular case, on CX1 copying the original template over would work while that is not possible in CX2.
For cases where templateData is missing, Content Translation can consider matching the existing parameters by name as a fallback approach.
In this process we need to make sure that we avoid using inexistent parameters on the target template (as described in T199308: CX2: Avoid using inexistent parameters when mapping template parameters)