I have one additional piece of information that might help diagnose the problem:

The fields that are being combined include the | delimiter in the output. It's as if the delimiter is being ignored.

Example:
Field 13 (EXTRA2) = test13
Field 14 (EXTRA3) = test14
Field 15 (EXTRA4) = test15
Field 16 (EXTRA5) = test16

The template output I'm getting is...
<%extra2%> = test13|test14|test15|test16
<%extra3%> thru <%extra5%> are all blank.