It looks like all of the affected DLG files contain one or more script structures (i.e. state trigger, transition trigger or action table structures) with their "Length" field set to 0. The
DLG format definition in IESDP is open to interpretation in this matter, so I'm not sure if these are valid structures or not.
Near Infinity is treating these cases as invalid and I haven't found a DLG file affected by this issue in any unmodded game yet. On the other hand, the games don't seem to crash or behave unusual when triggering the affected dialogs. I can try to add a fix or work-around in Near Infinity, but I don't know if or when I'll be successful as it touches a fundamental design aspect of NI. Maybe WeiDU's dialog compiler can be changed to preserve empty script structures by adding a single newline or space character.