b7907f8 created the issue

When syncing large directories with many subfolders via SFTP scanning of the directories will eventually halt for no apparent reason. If syncing is repeated with a significantly smaller folder containing the same directory which initially caused the failure, the problem will not be reproduced. Therefore, the problem apparently is not related with certain subfolders or files but when a critical number of subfolders is reached.

The problem does not occur with version 3.2, while the issue is fully reproduced by nightly build 4990.