When integrating the SMARTDAC+ GX/GP series' communication channel data using TLOG.SUM, what happens if a communication error or other abnormality occurs resulting in data loss?

Integration continues, but its behavior changes depending on the Watchdog timer settings. For example, if using a preset value with the Watchdog timer, integration uses the preset value. If the Watchdog timer is not used, integration uses the previous value.
See “Watchdog timer” in section 1.16, ”Configuring Communication Channels (/MC option)” in GX10/GX20/GP10/GP20 Paperless Recorder User's Manual (IM 04L51B01-01EN) .