I have the same bug with my DL580 Gen8.
But HPE thinks, is not a bug, it's feature (!?!)
....
HPE CUSTOMER ADVISORY - Document ID: c05169530
RESOLUTION
These failed write messages occur when an application/service writes to the iLO 4 channel driver without adequate free channels available in iLO 4 to accept the write request.
These messages can be safely ignored as subsequent writes will be allowed once channels become open.