So glad Andrea asked this question as I was wondering if I missed anything.
I will check in x265 version 4.0 along with the patch Andrew provided as ffmpeg-7.0.patch6 to fix it tomorrow.
Also, a question for Andrew about F_scale: if there is a specific parameter setting that makes this not fail, it can be added to cinelerra-5.1/ffmpeg/plugin.opts. Currently there is a line "scale 200:100" in that file that sets width and height defaults. So if the parameter is in 7.0 as well as 7.1, we can set that now so it does not fail later.
And another question for Andrew, I thought in one of your emails you mentioned vf_filter or something like that that also might need to be patched. But I can not find that anymore.