I found a bug that only reproduces with a very specific set of prerequisites (all of the following must be true):

• file with CRLF endings
• file with no EOL/trailling newline (removed using a hex editor since vim always adds them back)
• file larger than 32768 bytes
• CSV.foreach
• option strip: true
• option skip_lines: /\A,+\n?\z/

The following example (where original.csv is a file containing the line AAAA1234567890 ~2500 times):

CSV.foreach('original.csv', strip: true, skip_lines: /\A,+\n?\z/) do |data|
  puts data[0]
end

will print the last line duplicated:

AAAA1234567890
AAAA1234567890
AAAA1234567890
AAAA1234567890
AAAA1234567890AAAA1234567890
...

As a workaround I used CSV.parse(File.read, ...) with the same options, but I still wanted to flag this issue.