Iphone 6s Plus: Stuck in Recovery Mode. Upgrade via Win10 itunes does not complete.

During IPhone Maintenance Mode update of Software iOS 14.2 (4649850 Bytes in AppData Roaming Apple Computer iTunes iPhone Software Updates) stops with error (14). Win10 client is connected to Network! iPhoneUpdate Logs file shows the following errors:

[11:00:45.0905] ASR progress: Sending payload

[11:00:56.0065] <Restore Device 0000025107CCA8A0>: operation 13 progress 71

[11:00:56.0065] ASR progress: Sending payload

[11:01:12.0732] <Restore Device 0000025107CCA8A0>: operation 13 progress 72

[11:01:12.0732] ASR progress: Sending payload

[11:01:37.0142] <Restore Device 0000025107CCA8A0>: operation 13 progress 73

[11:01:37.0142] ASR progress: Sending payload

[11:01:44.0014] <Restore Device 0000025107CCA8A0>: operation 13 progress 100

[11:01:44.0014] ASR progress: Could not read all of client request

[11:01:44.0014] ASRServerHandleConnection failed: 2

[11:01:44.0014] AMRAuthInstallDeletePersonalizedBundle

[11:01:44.0123] <Restore Device 0000025107CCA8A0>: Restore failed (result = 14)

[11:01:44.0123] Restore completed, status:14

[11:01:44.0123] Restore Checkpoint Fingerprint: 065B.0000

[11:01:44.0123] Failure Description:

[11:01:44.0123] Depth:0 Code:-1 Error:AMRestorePerformRestoreModeRestoreWithError failed with error: 14

[11:01:44.0123] Depth:1 Code:14 Error:Failed to handle data request message

[11:01:44.0123] Depth:2 Code:14 Error:Failed to handle image request

[11:01:44.0123] Can't send dump_console command since device is not in recovery mode

[11:01:44.0123] AMRestorePerformRestoreModeRestoreWithError failed with error: 14

[11:01:44.0123] Finished RestoreOS Restore Phase: Failed

[11:01:44.0123] State Machine Dump, status:ERROR - [state:Recovery remaining-cycles:0] -> [state:RestoreOS remaining-cycles:0 (current state)]

[11:01:44.0123] Changing state from 'Restoring' to 'Error'

[11:01:44.0123] State is now set to error: AMRestorePerformRestoreModeRestoreWithError failed with error: 14

Iphone 6s Plus: Stuck in Recovery Mode. Upgrade via Win10 itunes does not complete. I have no complete backup as there iphone did not complete backup (not enough memory to backup).

iPhone OS (iOS) should be restorable without loosing data & Apps on iPhone but HOW?

iPhone OS (iOS) surely is stored in a different and secure location on the iPhone!