Cryptomator 1.9.1 write speed only 1 MiB/s

Cryptomator 1.9.1 writes only with 1 MiB/s speed. I am uploading archives (sizes are hundreds of MB - few GB) and it just won’t go any faster. Without cryptomator I am able to reach my upload limit speed (25 Mbit/s) without issues.

System with Windows 10, latest patches, CPU Intel Core i7-6700 quadcore with AES HW support…

Any ideas what could be the issue?

Thank you.

Further info. I use Total Commander to copy the files to the encrypted space.

Cryptomator shows a full upload speed of 25 Mbit/s (and 88 % cache usage), whereas Total Commander shows no progress. Then suddenly (once the full filesize of data has been transferred) in Total Commander status it shows as the file is transferred, however Cryptomator shows the speed of 1MiB/s.

I suspect Cryptomator creates a random data file with the full size on a remote filesystem first and then fills it with encrypted data? Why?