by Jodi Reed.
Did you ever find a solution?
I also have a teacher with this same error. I tried overwriting the TCPDF files and a number of other things, but nothing fixed it. FYI - this is not a problem for any of the other courses. This teacher used Reset on an old course -- got a TCPDF error for that too.
The only solution I found was to create a new course and then import the old course. The the user data was lost.