ffmpeg exited with code 1: Error initializing output stream 0:1 -- Error while opening encoder for output stream #0:1 - maybe incorrect parameters such as bit_rate, rate, width or height

[Treverr]

ffmpeg exited with code 1: Error initializing output stream 0:1 -- Error while opening encoder for output stream #0:1 - maybe incorrect parameters such as bit_rate, rate, width or height

[optio50]

Are you using the --he-audio option?
I also get this error with files that have AC-3 6 channel audio and trying to use opus HE audio.
The only workaround I found is to downmix the audio to Opus 2 channel or keep original audio.
--he-audio --downmix-he-audio

[optio50]

You could also convert just the audio to Opus before you use H265ize to avoid the error.
You can use this command.
ffmpeg -i 'InPut.mkv' -c:v copy -c:a libopus -b:a 256k -af aformat=channel_layouts="7.1|5.1|stereo" 'OutPut.mkv'

This should be a very quick process as you are only touching the audio in the video.
Then there is no need to use the --he-audio option for H265ize