Steps to Reproduce:

1. Create a Custom Field named 'Progress';
2. Add the field to a Screen;
3. Edit an issue and fill the 'Progress' field;
4. Go to the Issue Navigator and add the criteria for 'Progress';
5. Fill the form and hit Search.

Expected Results:

JIRA would return the issue matching the 'Progress' criteria.

Actual Results:

JIRA displays an error when trying to search:

When switching to Advanced Search, the same error is displayed:

Notes:

When making the search directly through the Advanced Search and using the Auto-Complete, JIRA replaces the name of the field (Progress) with cf[id]:

Workaround

Change the name of the Custom Field to something (slightly) different from 'Progress'.