{"error":"too_many_requests"} if i send to many pictures?

when i do a post, and try to send more than 3/4 pictures i get this error.

the only way to fix it is wait some minutes, edit the post and upload more images , just 1 or 2 more, before i get the same error {"error":"too_many_requests"}

is it lemmy.ml instance LIMIT by admin?