Cant export large folder to BIB or RIS either... :(

So following on to the column mangling of a csv export I thought I’d try exporting the same large (2016 papers) to a BIB or RIS file to see if I could work round the problem. The BIB file seems to export correctly, looking at it with a text editor file, it looks superficially ok, but it won’t import into EndNote. Nothing happens. It says it is going to import it but then nothing happens. I then tried importing the BIB file into Rayyan - and get an error message - “Unsupported file contents,” etc etc - It seems neither Evernote or Rayyan see the PaperPile export as a proper BIB file.

Trying a RIS file export, it starts, it seems to get somewhere, the I get the following error message:
“Something went wrong - The Chrome extension encountered a problem…etc etc”. I’ve tried reloading the extension (several times), removing and resetting it, opening new windows, all to no avail. What else can I try?