Some of these problems (roughly 100 out of 2000) use a macro called pccTables.pl, which lives in webwork-open-problem-library/OpenProblemLibrary/macros/PCC, and which actually just redirects to something called niceTables.pl, which currently lives in the develop branch of pg/macros. niceTables.pl assumes certain alterations have been made to the latex preamble for hard copies; changes that are part of the develop branch of webwork2.
Complicating things, at an earlier stage, a more primitive version of niceTables.pl was called pccTables.pl, and that pccTables.pl currently lives in the master branch of pg/macros. The problems may still function using this older pccTables.pl, but some may need the new pccTables.pl which is redirecting to niceTables.pl.
All this should be sorted out with a late winter 2.10 release. But in the mean time, trying to use the 100 or so problems that rely on niceTables.pl may cause you some headache.