NT151 xxx - SIII Master - configuration download fails.

NT151 PN IO Device - SIII Master (as well as all other combinations with SIII Master) - configuration download fails. Caused by error in download from SIII Master DTM.

1/ Drop NT151-XX-XX to the main bus line
2/ Port X2 -> PROFINET IO Device; port X3 -> SERCOS III Master
3/ Drop CIFX_RE_S3S_FIXCFG_1000_CIFX_RE_S3S_FIXCFG to SIII Master's bus line
4/ Assign the NT151 DTM to the NT151 device
5/ Do configuration download:

Result: download to Ch1 (SIII Master) fails with error "Download failed (General error during download) -> Device: netTAP[NT 151-RE-RE]<>(#1)".

6/ Without disconnecting the DTM - do 2 more download attempts - the same error again.
7/ Do one more attempt - now the download passes without an error!

OS: Windows 8.1
SYCON.net 1.500 Build 160107
SYCON.net 1.400 Build 160323
SYCON.net 1.500 Build 160504
SYCON.net V1.400 (Build 160607) with the attached firmware (PNS-S3M).

Note: The situation is also observed using SIII Master DTM and assigning it to Ch1 of NT151 device but happens sometimes and rarely.