Content Encoding Error when using a TLS certificate issued by Lets Encrypt

I get a Content Encoding Error in Firefox when trying to use a TLS certificate issued by Let's Encrypt.

Steps to upload it.

racadm -r ip -u root -p passwd --nocertwarn sslkeyupload -t 1 -f privkey.pem

racadm -r ip -u root -p passwd --nocertwarn sslcertupload -t 1 -f fullchain.pem

racadm -r ip -u root -p passwd --nocertwarn racreset

Access via IP is fine, but with Warnings

Access via racadm is fine but with warning: Security Alert: Certificate is invalid - unable to get local issuer certificate

Same error with wildcard and non-wildcard certificate.

IDRAC Version: 2.83.83.83 (Build 05)

Anyone else is having this issue?