Having trouble finding good vignetting correction figures for Lensfun in Hugin

lensfun
hugin
vignetting

#1

Here’s flat field image taken with Xiaomi Pocophone F1:

As you can see it suffers from rather pronounced vignetting, and for that I’m figuring out Lensfun correction parameters in Hugin. Usually Hugin has no problems solving the parameters from an image, but this time the best machine-optimized correction looks rather bad:

Any advice?