Index: trunk/src/org/openstreetmap/josm/io/BoundingBoxDownloader.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/BoundingBoxDownloader.java	(revision 10252)
+++ trunk/src/org/openstreetmap/josm/io/BoundingBoxDownloader.java	(revision 10253)
@@ -68,4 +68,6 @@
                     done = true;
                 }
+            } catch (OsmApiException ex) {
+                throw ex; // this avoids infinite loop in case of API error such as bad request (ex: bbox too large, see #12853)
             } catch (OsmTransferException | SocketException ex) {
                 if (isCanceled()) {