Jetty + HikariCP + JVM SSL Connectivity Issues to RDS PostgreSQL with RDS 2019 CA root certificate

I am having no luck in trying to connect to RDS PostgreSQL with Jetty (9.4.26) + JVM (java-1.8.0)

I have tried a few things

1. Importing 2019 RDS CA into Java cacerts
2. Setting up a separate TrustStore file for Java
3. Setting TrustStore file for Jetty in start.ini

Turning -Djavax.net.debug=ssl on shows that the 2015 RDS CA was added to trust, but I just cannot put a fingert as to where it is being told to trust. I am suspecting that the webapp has the 2015 RDS CA embedded...

Logs from Jetty

(-Djavax.net.debug=ssl)

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adding as trusted cert:
  Subject: CN=Amazon RDS Root CA, OU=Amazon RDS, O="Amazon Web Services, Inc.", L=Seattle, ST=Washington, C=US
  Issuer:  CN=Amazon RDS Root CA, OU=Amazon RDS, O="Amazon Web Services, Inc.", L=Seattle, ST=Washington, C=US
  Algorithm: RSA; Serial number: 0x42
  Valid from Thu Feb 05 20:11:31 AEDT 2015 until Thu Mar 05 20:11:31 AEDT 2020
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Jan 23, 2020 9:54:46 AM org.postgresql.Driver connect
SEVERE: Connection error: 
org.postgresql.util.PSQLException: SSL error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at org.postgresql.ssl.MakeSSL.convert(MakeSSL.java:67)
    at org.postgresql.core.v3.ConnectionFactoryImpl.enableSSL(ConnectionFactoryImpl.java:391)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:162)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195)
    at org.postgresql.Driver.makeConnection(Driver.java:452)
    at org.postgresql.Driver.connect(Driver.java:254)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:95)
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:101)
    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:314)
    at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:171)
    at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:441)
    at com.zaxxer.hikari.pool.HikariPool.access$300(HikariPool.java:66)
    at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:576)
    at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:569)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
    at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1946)
    at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:316)
    at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:310)
    at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1639)
    at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:223)
    at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1037)
    at sun.security.ssl.Handshaker.process_record(Handshaker.java:965)
    at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1064)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1367)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1395)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1379)
    at org.postgresql.ssl.MakeSSL.convert(MakeSSL.java:62)
    ... 18 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:397)
    at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:302)
    at sun.security.validator.Validator.validate(Validator.java:262)
    at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:330)
    at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:237)
    at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:132)
    at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1621)
    ... 26 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:141)
    at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:126)
    at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
    at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:392)
    ... 32 more
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Any ideas?