Picked up and installed Winclone 9 today so I could write to the BOOTCAMP partition. The mount read/write command gets a timeout error when I attempt it. As the error message suggested, I ran CHKDSK (no errors found) and I changed the sleep settings to NEVER while plugged in (the MacBook is currently running on line power). The BOOTCAMP disk icon disappears momentarily in the Finder, but reappears almost immediately, and after a few seconds, the error message pops up. Disk Utility can mount and unmount the BOOTCAMP partition just fine. The log shows this:
Additional Info: Error occurred at TCSPrivHelperToolController.m:497
2021-03-13T18:43:46-05:00:Mounting Error
2021-03-13T18:49:36-05:00:Winclone 9.0 (48405)
2021-03-13T18:49:36-05:00:Product ID:Winclone Standard
2021-03-13T18:49:36-05:00:Licensed to wmilliken@me.com
2021-03-13T18:49:36-05:00:License Key C8A-C5038C88-AE858A0F-7885738D-EC56C426
2021-03-13T18:49:36-05:00:Model Identifier: MacBookPro16,4
2021-03-13T18:49:36-05:00:=================diskutil list=================
2021-03-13T18:49:36-05:00:/dev/disk0 (internal, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *2.0 TB     disk0
1:                        EFI EFI                     314.6 MB   disk0s1
2:                 Apple_APFS Container disk1         1.4 TB     disk0s2
3:       Microsoft Basic Data BOOTCAMP                650.8 GB   disk0s3
/dev/disk1 (synthesized):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      APFS Container Scheme -                      +1.4 TB     disk1
Physical Store disk0s2
1:                APFS Volume Macintosh HD            11.2 GB    disk1s1
2:                APFS Volume Macintosh HD - Data     1.2 TB     disk1s2
3:                APFS Volume Preboot                 87.1 MB    disk1s3
4:                APFS Volume Recovery                528.9 MB   disk1s4
5:                APFS Volume VM                      1.1 GB     disk1s5
/dev/disk2 (external, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:     FDisk_partition_scheme                        *250.0 GB   disk2
1:                  Apple_HFS CoT-X1                  250.0 GB   disk2s1
2021-03-13T18:49:36-05:00:===============================================
2021-03-13T18:50:14-05:00:Mounting Error: An timeout occurred when mounting /dev/disk0s3. Please check that you can mount the volume in Disk Utility and try again
Additional Info: Error occurred at TCSPrivHelperToolController.m:497
2021-03-13T18:50:14-05:00:Mounting Error