Encounter sets are defined in Strange Eons in one of two ways
The first approach is preferable because
However the second approach is prevelant in user content as it is easier to find. Zoop handles these in different ways to group cards into encounter sets.
For 1 above identification is straightforward as all cards in the set are linked to the configured encounter set.
For 2 the only available data is a custom image path. Zoop takes the filename of this image (with the extension removed) and uses this to both assign a name to the encounter set and use it as the unique key for grouping.
The encounter set is relevant when
When 2 above is used the filename is used to derive the name of the encounter set. This may result in badly/incorrectly named encounter sets.
The recommended way of fixing this is to switch to option 1 above. Alternatively you can override the encounter set name by using an instruction