I ran into a very strange problem with the Merge Join.
I used two OLEDB Source objects to retrieve data from two databases. I used OLEDB source advanced properties to sort the output and ignore case (varchar data type).
I then added a Merge join object and used sorted output from OLEDB objects to perform matching. On 2 out of three servers this worked fine, but on one server 2 entries failed to match althought they were identical.
Replacing sorting in OLEDB source with Sort transformation fixes the problem.