mod_proxy_http2 + mod_proxy_connect prematurely closes connections (Apache HTTPD 2.4.62)

How to reproduce the issue:
1. install JBCS httpd 2.4.62 on RHEL8
2. copy the attached config files on RHEL8
3. modify /etc/hosts as follows:

127.0.0.1   fproxy.example.com host14.example.com localhost localhost.localdomain localhost4 localhost4.localdomain4

4. access the httpd as follows:

    h2load -c 1 -m 1 -n 1 https://host14.example.com/proxy/

or

    curl -v -k --http2 https://host14.example.com/proxy/

The connection from httpd to the forward proxy is not being kept alive. On the other hand, it is maintained in version 2.4.57.

Note: As of 9-May, testing confirms that this issue also affects the upstream 2.4.x branch.