Buddhism seemed problematic to Paul Williams because of the doctrines of rebirth and kamma, but in actuality it was Paul himself who let his view become problematic through worrying about death and beginnings; which in turn, demonstrates his inability to reach a full comprehension of the doctrines in both concept and practice. (as modus said). Paul also makes an emphais on the existence of self, " What is so terrifying about my being executed at dawn and reborn as a cockroach is that it is simply, quite straightforwardly, the end of me"- From this it seems Paul did not leave behind Buddhism because of the teachings themselves but rather his need for self-preservation and not clearly seeing that the ego is an illusion.
"A silver bird
flies over the autumn lake.
When it has passed,
the lake's surface does not try
to hold on to the image of the bird."