Hello,
there are no redirects configured in nginx.conf and the Lets Encrypt snippet is exactly the same as yours.
I can't post it here bc i would have to blackout so much stuff,.,,,GDPR
I can tell you it is a shared hosting system with a lot of Domains on it, and i am searching for this Error...
It may be "very unlikely" even that is not really a Professional answer.
If its unlikely, then plz explain why it works????
Automatic fails then i remove the "SEO redirect to HTTPS" do it again and it works...yeah very unlilkely.