Apache reverse proxy http2

Hello, I had a problem with my apache2 reverse proxy to openHAB since some times that I wanted to share.

When I enabled HTTP2 on my apache2 server the openhab web interface starts to behave strangely : everything shows normally but sometimes it takes several minutes. Trying to change an item results in : nothing happening.
Everything worked again flawlessly as soon as I added Protocols http/1.1 in the VirtualHost configuration.

My apache and openhab are on the same physical host by on different LXD containers.

Here is my complete VirtualHost config file :

<VirtualHost *:80>
    ServerName my.host.com
    RewriteEngine On
    RewriteCond %{HTTPS} off
    RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

<IfModule mod_ssl.c>
<VirtualHost *:443>
    Protocols http/1.1
    RequestHeader set X-Forwarded-Proto "https" env=HTTPS

    ProxyPreserveHost on

    LogLevel info warn

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    SSLCertificateFile /etc/letsencrypt/live/my.host.com/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/my.host.com/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/my.host.com/chain.pem
    Include /etc/letsencrypt/options-ssl-apache.conf
    ServerName my.host.com

    ProxyPass / ""
    ProxyPassReverse / ""

    <Location />
        AuthType Basic
        AuthName "tony"

        AuthUserFile /etc/apache2/htdigest_basic
        Require valid-user



Should I file a bug somewhere ? Is this issue already known ?