JabRef Always Opens in BibLaTeX Mode (BibTeX Mode Desired)

I am using JabRef 3.8.2 on Windows 10. I open a large (shared) reference database that nominally in BibTeX format (there may be a few entries that are in BibLaTeX format) upon startup. This always opens in BibLaTeX mode and I have to manually switch to BibTeX mode with File->Switch to BibTeX mode even though I have set the Preferences->General->Default bibliography mode to BibTeX.

Is there any way to fix this? I have tried resetting preferences to default, but this still happens. I suspect that there are some lingering settings from a previous JabRef version; I had JabRef 2.9 installed and after uninstalling from Programs & Features and then installing JabRef version 3.8.2, it launched and opened the bibliography file that I was previously using. However, I am not sure whether default bibliography mode was set in v2.9.

Issue resolved. This was due to @Comment{jabref-meta:databaseType:biblatex;} at the end of the .bib file. I checked the Database properties, but at least for V3.8.2, bibtex vs biblatex did not appear in this screen.