API: What would prevent an epic being returned as a parent or epic link of an issue?

[Steve Suranie]

I have a Python script that gets the child issues of an epic by returning issues that have an epic link or parent match. The JQL looks like this: 

https://xxxxxx.atlassian.net/rest/api/2/search?jql=project=KME AND "epic link" = 'Language Targeting' or parent = KME-79##

This is failing only on the above request. If I swap out the epic link and parent with others it works as expected. Is there something in the epic itself that could impact this? 

Edit: 
When I run the query through the browser it also fails: 

{"errorMessages":["No issues have a parent epic with key or name 'Language Targeting'"],"warningMessages":[]}

This query returns results: 

https://xxxxxxx.atlassian.net/rest/api/2/search?jql=project=KME AND "epic link" = 'Support for video ad duration' or parent = KME-80##

{"expand":"schema,names","startAt":0,"maxResults":50,"total":3,"issues":[{"expand"...

Edit Edit: The epic in question does have children, about 15 of them.

[Gonchik Tsymzhitov]

Hello  @Steve Suranie  , 

I have released a new version it will include that parent ticket info