To reproduce the problem: wget https://sources.debian.net/data/main/s/synfigstudio/1.0-1/images/animate_mode_icons.sif synfig -q animate_mode_icons.sif -o animate_mode_off_iconxx.png --time 0
Replacing /usr/lib/aarch64-linux-gnu/libsigc-2.0.so.0.0.0 with file from rebuilt libsigc++-2.0 fixes it.
