Error "java.sql.SQLRecoverableException: IO Error: Connection reset" or "java.sql.SQLRecoverableException: Closed Connection" thrown for various operations in Windchill PDMLink

• "java.sql.SQLRecoverableException: IO Error: Connection reset" error thrown for various operations
• "java.sql.SQLRecoverableException: Closed Connection" thrown for various operations
• Reference Designator column showing "???referenceDesignatorDU??? " randomly when comparing BOM 
• stack trace:

2023-08-16 03:27:11,132 ERROR [com.ptc.core.components.dataUtilities.worker-6457] wt.pds.exception <username> - Suppressing internal message (wt.pom.pomResource/0) wt.pom.PersistenceException: A persistence error occurred. System message follows:
Nested exception is: wt.pom.DatastoreException: A SQL error has occurred for the statement "SELECT ... Database system message follows:
Nested exception is: java.sql.SQLRecoverableException: Closed Connection
	at oracle.jdbc.driver.PhysicalConnection.prepareStatementInternal(PhysicalConnection.java:1812)
	at oracle.jdbc.driver.PhysicalConnection.prepareStatement(PhysicalConnection.java:1763)
	at oracle.jdbc.driver.PhysicalConnection.prepareStatement(PhysicalConnection.java:1755)
	at oracle.jdbc.driver.PhysicalConnection.prepareStatement(PhysicalConnection.java:1663)
	at wt.pom.BasicStatementManager._prepare(BasicStatementManager.java:89)
	at wt.pom.StandardCacheStatementManager.prepare(StandardCacheStatementManager.java:99)
	at wt.pom.WTConnection.prepareStatement(WTConnection.java:738)
	at wt.pds.BasicStatementBuilder.getStatement(BasicStatementBuilder.java:395)
	at wt.pds.BasicStatementBuilder.getStatement(BasicStatementBuilder.java:167)
	at wt.pds.AbstractResultCursor$1.getStatement(AbstractResultCursor.java:530)
	at wt.pds.AbstractResultCursor.executeQuery(AbstractResultCursor.java:549)
	at wt.pds.AbstractResultCursor.executeQuery(AbstractResultCursor.java:544)
	at wt.pds.BasicResultCursor.getNextResultSet(BasicResultCursor.java:282)
	at wt.pds.BasicResultCursor.advance(BasicResultCursor.java:234)
	at wt.pds.BasicResultCursor.next(BasicResultCursor.java:82)
	at wt.pds.SQLDatabasePds.query(SQLDatabasePds.java:880)
	at wt.pom.PersistentObjectManager.query(PersistentObjectManager.java:1077)
	at wt.fc.StandardPersistenceManager._query(StandardPersistenceManager.java:1977)
	at wt.fc.StandardPersistenceManager.query(StandardPersistenceManager.java:1929)
	at com.ptc.core.query.server.impl.BasicQueryService.execute(BasicQueryService.java:2076)
	at com.ptc.core.query.server.impl.BasicQueryService.query(BasicQueryService.java:580)
	at com.ptc.core.query.server.impl.BasicQueryService.query(BasicQueryService.java:856)
	...