A sampling of the closed headful clipboard tests that fail (not always) are :
Windows :
java/awt/datatransfer/ClipboardPerformanceTest/ClipboardPerformanceTest.html
java/awt/Clipboard/PasteNullToTextComponentsTest/PasteNullToTextComponentsTest.html
java/awt/Clipboard/ImageTransferTest/ImageTransferTest.html
java/awt/Clipboard/HTMLTransferTest/HTMLTransferTest.html
java/awt/Clipboard/ClipboardSecurityTest/ClipboardSecurity.html

Linux:
java/awt/Clipboard/ImageTransferTest/ImageTransferTest.html
java/awt/Clipboard/HTMLTransferTest/HTMLTransferTest.html
java/awt/Clipboard/ClipboardSecurityTest/ClipboardSecurity.html

macOS:
java/awt/Clipboard/PasteNullToTextComponentsTest/PasteNullToTextComponentsTest.html
java/awt/Clipboard/NoOwnerNoTargetsTest/NoOwnerNoTargetsTest.html
java/awt/Clipboard/NoDataConversionFailureTest/NoDataConversionFailureTest.html
java/awt/Clipboard/LostOwnershipChainTest/SystemClipboard2ProcTest/SystemClipboard2ProcTest.html
java/awt/Clipboard/ImageTransferTest/ImageTransferTest.html
java/awt/Clipboard/HTMLTransferTest/HTMLTransferTest.html
java/awt/Clipboard/GetAltContentsTest/SystemClipboardTest/SystemClipboardTest.html
java/awt/Clipboard/ClipboardSecurityTest/ClipboardSecurity.html

Keep this bug open until all of these are resolved potentially under other bug ids.