R Markdown Error reading bibliography: pandoc document conversion failed with error 25

Question

pandoc seems to have a problem with reading my bib file giving me this error:

Error reading bibliography file library.bib:
(line 19001, column 1):
unexpected "@"
expecting space, ",", white space or "}"
Error: pandoc document conversion failed with error 25
Execution halted

I am using Mendeley to produce my library.bib and the file includes all of my references (almost 30 thousand lines). When I search the line in question, everything seems to be in order (no unusual characters). Deleting the reference doesn't help. The "@" from the error is at the beginning of every reference in the file. Using a smaller subset of my reference list from another folder doesn't help, I only managed to knit my document with a very small subset (1000 lines). The library.bib is a copy in my project folder so it is not influenced by running Mendeley.

I can make a subfolder with references needed for this only document but it doesn't provide a long-term solution - I would like to use the whole library and not make a subfolder for each document I am working on.

Is there something simple I am missing? Thanks!