Vbseo causing avatar not to appear

Hi, many users when they upload their avatar, their avatar does not show up

it shows a blank pic, this happened all of a sudden, i never experience this bug before, when i ticked vb and they suggested to disable all my addon,

Hi there;
It seems like the image is not being written there properly. Your image processor seems to be working properly though:

Please check if you installed any addon that deals with user avatars or image manipulation (watermarking maybe?), and try to disable that to see if that resolves the problem for you.

i disable one by one till i found that when i disable my vbseo xml, the avatar appears. How can i fix this bug?

Edit:

it seems that disabling this function fix the issue, why is that?

Custom Avatar Image URLs [disable]

Rewrite Custom Avatar URLs?
Set this option to "Yes" to have custom avatar URLs rewritten.

Yes it's fixing after disable it that's because the Avatar URL Format
you can enable it again and choose "[user_id].gif"