Text critics have always found lots of work to do in the Jesus sayings dealing with divorce. More recently, however, the difficulty of work has increased significantly, with serious ramifications for our traditional view of Canon. This comes as a result of David C. Parker's short book, The Living Text (1997).
Here is Eldon Epp's explanation of the issue:
"[Another] more poignant example in its relevance to anguishing life situations concerns the twenty-some [emphasis added] variants in the four passages on divorce/remarriage in the Synoptic Gospels. Parker's analysis of this complex array shows that some variants concern Jewish, others Roman provisions for divorce; some condemn divorce but not remarriage, while others prohibit remarriage but not divorce; some variants describe adultery as remarriage, others as divorce and remarriage, and others as marrying a divorced man; and some variants portray Jesus as pointing to the cruelty of divorcing one's wife--thereby treating her as if she were an adulteress, though she was not--perhaps with the outcome of establishing her right to remain single, yet without affirming that the divorcing man commits adultery. Some variants, therefore, are concerned with the man, others with the woman, and still others with both. Sometimes the divorcing man commits adultery, sometimes not; sometimes the divorced or divorcing woman commits adultery, sometimes she is made an adulteress, sometimes she commits adultery if she remarries, and finally, sometimes a man marrying a divorced woman commits adultery" ("The Oxyrhynchus New Testament Papyri: 'Not without honor except in their hometown'?" JBL 123 (2004) pp. 7-8 [cf. rpt in Perspectives on New Testament Textual Criticism: Collected Essays, 1962-2004, pp. 745-746]).
In this light, must we despair of ever finding out the original text in Matthew, Mark or Luke? I'm not sure what the answer is, but the task before us is much more complicated now than it was 20 or 50 years ago. In our present situation, not only are we dealing with the issue of the New Testament text, but also with the New Testament Canon. We're facing major issues which beg for a resolution so that we don't give up the discipline to despair.