Hi,
the abstract of articles is added to the BibTeX-Export OJS in 3.1.2, but HTML-Tags are not removed (but encoded).
Could you, e.g., add a strip_tags to citationStyleLanguage/CitationStyleLanguagePlugin.inc.php at fa5b8a0fce8fd2bfa5cdd29abc81c7765900b4ce · pkp/citationStyleLanguage · GitHub?
If you have HTML-Tags in titles/subtitles the same problem arises for those metadata.
regards,
Carola