JQL search broken when indexing language is set to German

Issue Summary

When setting the indexing language to German, the JQL search does not work as expected.

For example, If there is an issue with the summary "Test DA".

The JQL Query "summary ~ Test" will return the issue.
The JQL Query "summary ~ DA" will not return the issue ( occurs intermittently )

Steps to Reproduce

1. Create an issue with the summary as "TEST DA"
2. Change the Indexing language & Default language to German
3. Reindex the JIRA
4. Try to search the issue using "summary ~ DA" using the advance JQL search.

Expected Results

It should return the issue where the summary has the word DA

Actual Results

It intermittently returns results. Please refer to this video recording :
2020-08-04_15-49-05.mp4

From the logs we also see the same :

Workaround

We can currently use the escape sequence as given here :

summary ~ \"DA\"

Or continue to click the Search button until the results appear.