Synology PMS fails to transcode specific high bitrate HEVC 8bit content if HW encoding is enabled

Server Version#:1.15.8.1198 Synology on intel x64
i3-8100, local package install
Player Version#:3.102.0
chrome web

Direct streaming is fine. Other bit rate files are fine. Disable hw transcode and it is fine. Completely repeatable.

jellyfish-35-mbps-hd-hevc.mkv (HEVC/MAIN/4.1/HIGH) works fine.
jellyfish-40-mbps-hd-hevc.mkv (HEVC/MAIN/4.1/HIGH) works fine.
jellyfish-45-mbps-hd-hevc.mkv (HEVC/MAIN/4.1/HIGH) works fine.
jellyfish-50-mbps-hd-hevc.mkv (HEVC/MAIN/5.0/HIGH) fails to start.
jellyfish-55-mbps-hd-hevc.mkv (HEVC/MAIN/5.0/HIGH) works fine.
jellyfish-60-mbps-hd-hevc.mkv (HEVC/MAIN/5.0/HIGH) works fine.

The file does not appear to be corrupt, MKVtools doesn’t indicate an issue, and it plays locally just fine.

Not just this server/client version, I have seen this error for months of revisions.