sorry, missing one line in the test script:

Here's the correct one:
-------------------

$servers = [ '192.0.2.1', '192.0.2.2', '192.0.2.3' ];

foreach ($servers as $server) {

$resolveparam = [ 'example.com:443:'.$server ];

$ch = curl_init();

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_DNS_CACHE_TIMEOUT, 0);
curl_setopt($ch, CURLOPT_RESOLVE, $resolveparam);
curl_setopt($ch, CURLOPT_URL, "https://example.com/some/path");
curl_setopt($ch, CURLOPT_VERBOSE, 1);

$result = curl_exec($ch);
$info = curl_getinfo($ch);

echo $info['primary_ip']."\n";
curl_close($ch);
}

It's a bit tricky but isn't related to PHP Curl lib.
According to libcurl documentation (https://curl.haxx.se/libcurl/c/CURLOPT_RESOLVE.html) 

"Remove names from the DNS cache again, to stop providing these fake resolves, by including a string in the linked list that uses the format "-HOST:PORT". The host name must be prefixed with a dash, and the host name and port number must exactly match what was already added previously."

so you can use something as following to perform what you want:

$resolveparam = [ $prev_server ? '-example.com:443:'.$prev_server : '', 'example.com:443:'.$server ];
    $prev_server = $server;

Cannot reproduce either.

* Added example.com:443:192.0.2.1 to DNS cache
* Hostname example.com was found in DNS cache
*   Trying 192.0.2.1...
* TCP_NODELAY set
* Connection timed out after 1001 milliseconds
* Closing connection 0

* Added example.com:443:192.0.2.2 to DNS cache
* Hostname example.com was found in DNS cache
*   Trying 192.0.2.2...
* TCP_NODELAY set
* Connection timed out after 1001 milliseconds
* Closing connection 0

* Added example.com:443:192.0.2.3 to DNS cache
* Hostname example.com was found in DNS cache
*   Trying 192.0.2.3...
* TCP_NODELAY set
* Connection timed out after 1001 milliseconds
* Closing connection 0

That was fixed in curl 7.61
https://github.com/curl/curl/pull/2622

but don't work in older versions.

Ondrej ppa for ubuntu still has old one.

Workaround is trivial:

CURLOPT_RESOLVE => ['-manychat.com:80', 'manychat.com:80:18.185.191.84']


will clear previous value if any and provide the new one.