Rarely, a situation can happen where TFTP will timeout when requesting the boot files during PXE boot.
PXE-E32: TFTP open timeout
A bug was discovered that on occasion when a boot file is requested and the response is 'Not Ready' on the file on the backend of the TFTP server, every additional check to see if the file is ready would return 'Not Ready' even when the files became available to the service.
This issue is fixed in DS 7.6 HF7 via a new build of the TFTP server. A build will become available attached to this article shortly.