Compiling from master doesn't generate bootable Khadas Vim2 images / kernels

I just compiled a fresh image from master for the Khadas Vim2 box which is running on a year old version. At the moment it doesn't generate a bootable image (no special settings, just running the PROJECT=Amlogic ARCH=aarch64 DEVICE=AMLGX UBOOT_SYSTEM="khadas-vim2" make image I was using before; screen remains black, white LED on, no USB input). I checked with the running version by just replacing the system and kernel with the freshly compiled one, same result (moving the stuff back, produces a working system again). Other recent images boot, like the latest oowow and Armbian (November last year). I think I tried a new build in last August and already failed with the same result (but didn't have time to investigate, but simply switched back to the working image). Any ideas what I do wrong here?