Dimension restrictions for nvh265enc/nvh264enc?

I am writing custom processing logic that feeds buffers into the encoder via appsrc. I kept getting QoS messages from the encoder element when feeding in a buffer with size 1444x952 stating that the buffers were being dropped.

However, when I used the same code and rescale the image to 2160x1440, it works great.

Are there restrictions on the image width/height for these hardware encoders?

Looks like the width & height must be divisible by 8? Is this requirement documented somewhere?