Hello,
Its hard to tell what the issue could be. Can you give more information on how you setup your environment? If your unsure what to post, this post will help us, help you.
EDIT: Sorry I missed this question
1.Input types/configurations
2.Log shipper version/type/configuration
3.extractors or pipelines created
4.Logs Elasticsearch/Graylog ( basically look for anything that would pertain to this issue)
5.What type of input are for what type of devices in this environment.
Sum it up, demonstrate how your ingesting logs from a remote device to Graylog.
In that post above it shows how/what to use when posting logs files and/or configuration files.