If I open a file from the "Files" tree in an editor (via double click or "Open" action from the contextual menu menu), debugging shows that the PaneFactory.createNBEditorPane() is called twice with different JEditoPane instances, and between these calls there is a PaneFactory.closePane() call which releases the first JEditorPane instance. This means that the first instance is not shown in the GUI and there is no need to instantiate it.

If I open a file from the "Projects" tab, there are no such redundant calls, i.e. the issue doesn't occur here.

The redundant calls are (tested with rc-14 build):

com.aquafold.editor.standalone.api.PaneFactory.createNBEditorPane(PaneFactory.java:442)
com.aquafold.aquaeditor.bridge.PaneFactory.createNBEditorPane
com.aquafold.aquaeditor.bridge.PaneFactory.createNBEditorPane
\\...\\ .\\हिñçêČάй語简�?한\\._ꌪꍎ⢇ꌀ.a
\\...\\ .\\हिñçêČάй語简�?한\\._ꌪꍎ⢇ꌀ.<init>
\\...\\ .\\हिñçêČάй語简�?한\\.vᚦꄴ᠁ᡓ 3 void.a
\\...\\ .\\हिñçêČάй語简�?한\\.vᚦꄴ᠁ᡓ 3 void.a
\\...\\ .\\हिñçêČάй語简�?한\\.Oꎼ⡯⣟⡳.a
\\...\\ .\\हिñçêČάй語简�?한\\.F᠏ꂠꎏ̨ if for.a
com.aquafold.datastudio.mainframe.ActionHandler.actionPerformed
javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2012)
javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2335)
javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:404)
javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
javax.swing.AbstractButton.doClick(AbstractButton.java:374)
javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:829)

and

com.aquafold.editor.standalone.api.PaneFactory.closedPane(PaneFactory.java:701)
\\...\\ .\\हिñçêČάй語简�?한\\.ěꏴ⡼ꆫ.a
\\...\\ .\\हिñçêČάй語简�?한\\._ꌪꍎ⢇ꌀ.a
\\...\\ .\\हिñçêČάй語简�?한\\._ꌪꍎ⢇ꌀ.<init>
\\...\\ .\\हिñçêČάй語简�?한\\.vᚦꄴ᠁ᡓ 3 void.a
\\...\\ .\\हिñçêČάй語简�?한\\.vᚦꄴ᠁ᡓ 3 void.a
\\...\\ .\\हिñçêČάй語简�?한\\.Oꎼ⡯⣟⡳.a
\\...\\ .\\हिñçêČάй語简�?한\\.F᠏ꂠꎏ̨ if for.a
com.aquafold.datastudio.mainframe.ActionHandler.actionPerformed
javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2012)
javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2335)
javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:404)
javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
javax.swing.AbstractButton.doClick(AbstractButton.java:374)
javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:829)