NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9800)

Question

I am really frustrated with the situation I am facing right now. Some help would be greatly appreciated.

When sending POST request via URLSession, it gives NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9800) error.

I am using GoDaddy SSL certificate, and the website shows secure on the far left corner with no problem when accessing.

The error above happens once in a while. The above error does not happen every time I send the request. My app is sending a request every second to poll new data.

I assume the problem could be due to sending so many requests in short period of time. I am not entirely sure if this is the case.

I am using Tomcat as the web server and catalina.out does not show anything wrong with this.

To see what could have gone wrong, I ran diagonostics through

nscurl --ats-diagnostics https://***

Result is as following:

Configuring TLS exceptions for ***
---
TLSv1.3
2018-05-16 11:35:00.691 nscurl[92034:10819554] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9800)
Result : FAIL
---

Configuring TLS exceptions with PFS disabled for ***
---
TLSv1.3 with PFS disabled
2018-05-16 11:35:01.273 nscurl[92034:10819468] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9800)
Result : FAIL
---

Configuring TLS exceptions with PFS disabled and insecure HTTP allowed for ***
---
TLSv1.3 with PFS disabled and insecure HTTP allowed
2018-05-16 11:35:01.591 nscurl[92034:10819579] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9800)
Result : FAIL
---`

Everything else passes.

What I have tried to mitigate the problem. In Info.plist, I had uncommented those shown below. I also have tried arbitraryloads, but it does not work. In addition, arbitraryloads has some downsides regarding security, so I want to avoid using this as much as possible

<key>NSAppTransportSecurity</key>
    <dict>
<!--        <key>NSExceptionDomains</key>-->
<!--        <dict>-->
<!--            <key>***</key>-->
<!--            <dict>-->
<!--                <key>NSExceptionRequiresForwardSecrecy</key>-->
<!--                <false/>-->
<!--                <key>NSExceptionAllowsInsecureHTTPLoads</key>-->
<!--                <true/>-->
<!--                <key>NSExceptionMinimumTLSVersion</key>-->
<!--                <string>TLSv1.2</string>-->
<!--            </dict>-->
<!--        </dict>-->
    </dict>

Thanks for taking your time to read my question (major problem for me)