The 'Server communication problem. Please try again' message is appeared in Inventory app after clicking on the 'Export instances (MARC)' button

Steps to Reproduce:

1. Log into bugfest environment as admin.
2. Go to Inventory app.
3. Find one or more Source = MARC records in Inventory.
4. Mark the checkbox next to a few of the MARC records in the list.
5. Click Actions/Export Instances (MARC).
6. Pay the attention on the displayed message. 

Expected Results: File with name quick-export-[number].mrc is at the top of the export log.
Actual Results: The 'Server communication problem. Please try again' message is appeared in Inventory app after clicking on the 'Export instances (MARC)' button.