I updated my Sailfish Application SDK to include the brand-new 4.0.1.48 build, no issues there. Then I noticed that it had dropped my aarch64 build target, so I restarted the maintenance tool, selected it, started the installation, and it errored out:
Preparing the installation...
Downloading packages...
Downloading archive "2021.02.11-1Sailfish_OS-4.0.1.48-Sailfish_SDK_Target-aarch64.tar.7z.sha1"
for component SailfishOS-latest-aarch64 (4.0.1.48).
Downloading archive "2021.02.11-1Sailfish_OS-4.0.1.48-Sailfish_SDK_Target-aarch64.tar.7z" for
component SailfishOS-latest-aarch64 (4.0.1.48).
Installing component SailfishOS-latest-aarch64 (4.0.1.48)
Extracting "2021.02.11-1Sailfish_OS-4.0.1.48-Sailfish_SDK_Target-aarch64.tar.7z"
The command needs to be used under Sailfish SDK workspace, which is currently configured as
"/home/direc85/SFOS"
I started the maintenance tool from the .desktop file as usual, and it has worked quite reliably for me.