My system stayed on the same version of Balena 1.5.52, and started having this problem after a features update to Windows10, version 1903 was installed on August 19, 2019. After allowing the access in the Windows 10 dialog after clicking Flash, Etcher reports the error seen in the first entry here: Etcher 1.5.5 windows, writer process problem
After that, a Microsoft notification appears that an attempt to change was blocked. The Protection history gets an entry which says Protected folder: \Deivce\Harddisk3\DR5, Blocked by: Controlled folder access.
Obviously, the only listed folders to be protected are C:\Users{user}… Documents, Music, etc, etc. Something in the update is clearly blocking more than they say. This update has added the phrase “ransomware protection” to their changes, so I suspect they are being very aggressive in what they block until people complain enough.
I’m not sure what you can do about this on your software, but I have a solution I may go to very soon: dump Windows. Microsoft is acting like a bully. This last update removed shortcuts I use on startup, and they had no notice they would do it, and no log of what they did remove. That is HIGHLY unprofessional.