ControlLogix Ethernet driver — repeated project upload failures / "device not responding" on legacy CompactLogix

Experiencing intermittent communication failures across multiple devices on the Allen-Bradley ControlLogix Ethernet driver.

Environment:

• Product: ThingWorx Kepware Server [version, e.g. 6.x — check Help → About]
• OS: [Windows Server version]
• Driver: Allen-Bradley ControlLogix Ethernet
• Affected devices: 1769-L23E-QBFC1 (CompactLogix 5323E), firmware revision 20.12, connected via embedded EtherNet/IP port, connection path <IP>,1,0
• At least 6 devices affected across multiple channels (CH_3, CH_4, CH_9, CH_13, CH_14, CH_15, CF_2), IPs in the 10.16.70.x range

Symptoms (from Event Log, 21/07/2026, 15:07–15:37):

• Warning: "The following errors occurred uploading controller project from device. Resorting to symbolic protocol." — repeating every ~10–15 seconds per device
• Warning: "Device is not responding. | ID = '<10.16.70.x>,1,0'."
• Warning: "Frame received from device contains errors." (device CH073, 10.16.70.114)
• Between failures, the driver successfully reads device identity (Details events return correct Vendor ID, Product code, Revision, S/N), indicating the connection is partially working

The pattern per device is: identity read succeeds → project upload fails ~3 seconds later → "Device is not responding" ~15 seconds after that → identity read succeeds again. The driver appears to be in a continuous retry loop re-attempting the controller project upload.