Help PVService error unless I reboot

Can someone offer some advice before I go completely mad.

THE SYSTEM
I have been running the PVoutput from my Samil inverter to an aged laptop or two for about 6 years.
One of them is running WinXP (PVbeancounter 1.xx), the other Win10 (PVbeancounter 2.xx). Both use the same PL2303 USB to Serial device as the Inverter has a serial connection. Eventually, after a couple of months the PVservice, although running, does not collect the data unless I reboot or refresh the Inverter connection in PVbeancounter.

If I completely rebuild the computer it will work again for another 2 months. This is why I have two.
I have tried different driver versions, different OS, and different beancounter versions.
I am hoping someone will be able to shed some light on this mystery. I am fed up of climbing into the loft to change computers etc

Here is a capture from the PVService Log.

26/05/2021 07:59:46 :T07 SAMILInverterManager :Finalise: Inverter Manager - Id = 2 - manager stopping
26/05/2021 08:00:07 :T18 SAMILInverterManager :Initialise: Inverter Manager - Id = 2 - manager running
26/05/2021 08:00:17 :T18 SAMILInverterManager :StartPortReader: Port: COM4 - Exception: Access to the port ‘COM4’ is denied.
26/05/2021 08:00:17 :T18 SAMILInverterManager :Finalise: Inverter Manager - Id = 2 - manager stopping
26/05/2021 08:00:37 :T13 SAMILInverterManager :Initialise: Inverter Manager - Id = 2 - manager running
26/05/2021 08:00:47 :T13 SAMILInverterManager :StartPortReader: Port: COM4 - Exception: Access to the port ‘COM4’ is denied.
26/05/2021 08:00:47 :T13 SAMILInverterManager :Finalise: Inverter Manager - Id = 2 - manager stopping
26/05/2021 08:00:53 :T20 :PVService: Shutdown initiated
26/05/2021 08:01:54 :T04 :PVService: Start requested

Timeline Content

Start: 00:00:00 - End: 23:59:00 - Running - EveningSuspend


26/05/2021 08:01:54 :T05 ExecutionManager :: PVService - version:1.9.0.10
Log Settings

      Log Trace: Off
Log Meter Trace: Off

Log Message Content: Off
Log Database: Off

26/05/2021 08:01:55 :T05 ExecutionManager :ExecutionStateManager: State: Running
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: StartService: connecting to database: Data Source=C:\PVRecords\pvhistory.s3db
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Loading Event Manager
26/05/2021 08:02:15 :T08 EventManager :EventManager: Initialise - Energy Manager running
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Event Manager Loaded
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Loading Inverter Managers
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: NextFullDay set to no older than 24/05/2021 00:00:00 for manager Id 2
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManager: Id = 2 loaded
26/05/2021 08:02:15 :T07 SAMILInverterManager :Initialise: Inverter Manager - Id = 2 - manager running
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Inverter Managers Loaded
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Loading Meter Managers
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Meter Managers Loaded
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: Loading PvOutput Managers
26/05/2021 08:02:15 :T05 ExecutionManager :InverterManagerManager: 1 PVOutput Managers Loaded
26/05/2021 08:02:15 :T04 PVOutput/13917 :Initialise: pvoutput.org update started
26/05/2021 08:02:46 :T05 ExecutionManager :ExecutionStateManager: State: Running
26/05/2021 08:04:07 :T04 PVOutput/13917 :LoadPVOutputBatch: pvoutput.org batch updated - DataPoints: 91 - Hour Total: 4 - Limit: 60
26/05/2021 08:04:15 :T07 SAMILInverterManager :StartPortReader: Port: COM4 - Exception: Access to the port ‘COM4’ is denied.
26/05/2021 08:04:15 :T07 SAMILInverterManager :Finalise: Inverter Manager - Id = 2 - manager stopping
26/05/2021 08:04:16 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:15 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 0 - Power: 0 - Energy: 0
26/05/2021 08:04:16 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:15 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 0 - Power: 0 - Energy: 0
26/05/2021 08:04:16 :T14 SAMILInverterManager :Initialise: Inverter Manager - Id = 2 - manager running
26/05/2021 08:04:17 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:16 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 0 - Power: 0 - Energy: 0
26/05/2021 08:04:19 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:16 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 0 - Power: 0 - Energy: 0
26/05/2021 08:04:22 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:22 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 6 - Power: 573 - Energy: 0.000955
26/05/2021 08:04:24 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:22 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 6 - Power: 573 - Energy: 0.000955
26/05/2021 08:04:26 :T14 SAMILInverterManager :StartPortReader: Port: COM4 - Exception: Access to the port ‘COM4’ is denied.
26/05/2021 08:04:26 :T14 SAMILInverterManager :Finalise: Inverter Manager - Id = 2 - manager stopping
26/05/2021 08:04:28 :T03 DeviceMgr_COM4 :EnergyEvents: NewEnergyReading - Event Type Not Found - time: 26/05/2021 08:04:28 - Type: Yield - Manager: DeviceMgr_COM4 - Component: S44127R473 - Device: - Interval: 6 - Power: 575 - Energy: 0.000958333333333333