If it's use case C, please check first, if the LFW version is compatible with MFW version:
Which Maintenance Firmware is compatible to which protocol firmware (netX90 Use Case C)? Maintenance Firmware(MFW) V1.3.0.0 and higher version has Flash Translation Layer (FTL) intergated, which is incompatible to earlier versions, so a full format request (HIL_FORMAT_REQ) is required in this case when the MFW is downloaded to INTFALSH01 and run for the first time. The full format takes about 1 or 2 minutes, and the SYS led blinks green during the period. 
If an ERR_HIL_FIRMWARE_STARTUP_ERROR (0xC0000129) returns not caused by flash file system(FFS) issue, then it could be something wrong with the hardware configuration file (*.hwc or *.mwc). Please check the configuration of your hardware config file (*.xml), and "Build Hardware Configuration..." to create the *.hwc and *.mwc with the latest netX Studio CDT tool, which integrates the current version of the hardware config tool.
https://kb.hilscher.com/display/NDT Sometimes, the ERR_HIL_FIRMWARE_STARTUP_ERROR returns, if the uart firewall is not set correctly. E.g. If you set APP has read/write access, then you must disable uart 0 of LFW via taglist editor.
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