Reduce and rebuild the range

1. Record the successful and unsuccessful requests, including Unit ID, function, start offset, quantity, and error.
2. Check every address in the larger range against the field-device map. A gap between valid points can make the complete request fail.
3. Check the field device's documented maximum block size. The protocol allows up to 125 registers for FC03/04, but a particular device can impose a smaller supported range or quantity.
4. Preserve complete values and required alignment. Some devices serve only complete two-register values; splitting them into single-register tests can also fail.
5. Turn off or limit the external driver's automatic block merging while isolating the range, if the driver provides that option.
6. Increase the range only within documented contiguous areas. Confirm the SB1000 firmware version if valid large reads fail; its release history includes TCP framing and full-size-read corrections in firmware 7.

Firmware with RS485 Register scan offers an optional paired-reading mode for suitable devices. A scan's successful words do not establish that every arbitrary merged block is supported.

Expected result

Each configured block returns the expected quantity without exceptions or timeouts. Report the smallest failing block and the map excerpt if a documented request still fails.