I've recently upgraded my Indigo platform which has been running happily since 2014 or so.
Old: a well-worn Mac mini(2,1) with OSX 10.7.5 (Lion) and Indigo 6.1.11
New: a newer Mac mini (2.3 GHz Intel Core i5) with macOS 10.13.6 (High Sierra) and Indigo 2022.2.
No change: Insteon PowerLinc 2413U modem and USB cable.
Since the migration, I'm finding several errors in the Event log every night at 11:45pm.
The errors are all "send failed (no acknowledgement)", occurring when Indigo sequentially sends OFF messages to various Insteon lights and outlets.
The cluster of errors occur nightly at 11:45pm, triggered by a scheduled event.
That event contains a single action:
Type: All Off (Light Appliance Controls)
Devices: All INSTEON/X10.
I have a few old X-10 devices, and 9 Insteon dimmers, switches, and outlets.
At 11:45pm, the log shows the server sends an X10 command to turn all units off. There's no response nor error since X10 is a one-way protocol.
The server then appears to send sequential OFF messages to the 9 Insteon devices.
Some result in "no acknowledgement" errors. It seems random which devices succeed and which result in an error.
I've done a bunch of manual testing, using both the Indigo Touch app on my iPhone and the Indigo 2022.2 app on my Mac to send ON and OFF commands to individual devices. No errors are generated. But like clockwork, every night the process by which the server executes the All INSTEON - OFF action leads to errors.
This behavior started after migrating to the new Indigo environment. I still have the old Mac mini on hand, and I've inspected the Indigo logs from before it went out of service. No errors were observed in the logs, going back several days..
So what's changed? The Mac mini hardware is new, and faster. Indigo 2022.2 is new. The underlying OS is new (now 10.13.6). And there's no add-on 3rd-party USB driver which was required with 10.7.
The logs also show occasional "send failed (no acknowledgement)" errors during the day, all triggered by various scheduled events. A few per day. I don't see any pattern as to time of day, or device.