I upgraded from 1.4.4 today and hit this issue. Last month I upgraded to Win 10 1809 and this is my first use after OS upgrade.
This is the relevant part from the console (happened for different images and sd-cards):
Tue Mar 05 2019 06:11:49 GMT+0300 (Turkey Standard Time) Flash error ({“error”:{“name”:“Error”,“message”:“EPERM: operation not permitted, write”,“stack”:“Error: EPERM: operation not permitted, write”,“code”:“EPERM”,“syscall”:“write”,“errno”:-4048},“applicationSessionUuid”:“8632f56a-7eec-4d6d-9916-81e6ff386c82”,“flashingWorkflowUuid”:“bb07637d-ebc8-492b-8a21-f126fc82a43d”,“flashInstanceUuid”:“84b2fd2c-8624-49be-b295-5eb4d08a628b”,“image”:“M:\__EX_SERVE_BACKUP_SYS_OLD\hkbox-os-images\OPi\PC2\Armbian_5.75_Orangepipc2_Ubuntu_bionic_next_4.19.20_desktop.img”,“drives”:[{“size”:31914983424,“isVirtual”:false,“enumerator”:“USBSTOR”,“logicalBlockSize”:512,“raw”:“\\.\PhysicalDrive7”,“error”:null,“isReadOnly”:false,“displayName”:“U:\”,“blockSize”:512,“isSCSI”:false,“isRemovable”:true,“device”:“\\.\PhysicalDrive7”,“busVersion”:“2.0”,“isSystem”:false,“busType”:“USB”,“isCard”:false,“isUSB”:true,“devicePath”:null,“mountpoints”:[{“path”:“U:\”}],“description”:“Generic MassStorageClass USB Device”,“isUAS”:false}],“driveCount”:1,“uuid”:“84b2fd2c-8624-49be-b295-5eb4d08a628b”,“unmountOnSuccess”:true,“validateWriteOnSuccess”:true})