I have the same exact issue during order process after payment.
Already verified /includes/tcpdf.php, /includes/pdfconfig.php and /templates/mytemplate/quotepdf.tpl are correct.
Our logo is a gif file and this is reflected in the configuration and files listed above but still get the same error
TCPDF error: Missing or incorrect image file: /home/user/public_html/templates_c/jpgv54qbF
File exists but is 0 byte
-rw------- 1 user user 0 Jun 25 19:34 jpgv54qbF