This field shall be set to the number of bytes that have been downloaded during the failing transfer that caused this event to be generated.
This field SHOULD be set to some internal product-specific error code, closest in temporal/functional proximity to the failure that caused this event to be generated. Otherwise, it shall be null. This event field may be used for debugging purposes and no uniform definition exists related to its meaning.
This field shall be set to the nearest integer percent value reflecting how far within the transfer the failure occurred during the failing transfer that caused this event to be generated, unless the total length of the transfer is unknown, in which case it shall be null.
This field shall be set to the value of the SoftwareVersion being downloaded, matching the SoftwareVersion field of the QueryImageResponse that caused the failing download to take place.
Body of the OtaSoftwareUpdateRequestor downloadError event
See
MatterSpecification.v13.Core § 11.20.7.7.3