Bulk upload stopped working

I have self-hosted Kaltura CE and just recently bulk upload stopped working. After uploading any CSV (manually or by API), I see “Verifying file” task status in bulk upload log. When I’m downloading bulk upload log file, it contains only “Log file is not ready”, though upload task already been there for half a day already.
Where can I check kaltura logs related to bulk uploading? I’ve checked “kaltura_api_v3.log”, “kaltura_prod.log”, “kaltura_apache_errors.log” - no recent errors there.