Hi,
There is a known issue in r36.4.7:
"unable to allocate CUDA0 buffer" after Updating Ubuntu Packages
And we would suggest base on r36.4.4 and rebuild kernel with the patches:
"unable to allocate CUDA0 buffer" after Updating Ubuntu Packages - #169 by AastaLLL
Or may stay on r36.4.4 and wait for next Jetpack 6 release.