I have some trouble with dbus-send when using a{sv}
dbus-send
a{sv}
Calling a method with in_signature=\'a{ss}\' seems to work using the followin
in_signature=\'a{ss}\'
You need to compile dbus-send with the following patch.
https://chromium-review.googlesource.com/#/c/12323/2/sys-apps/dbus/files/dbus-1.4.12-send-variant-dict.patch
FYR, I uploaded the patched full source at this link.
https://gitlab.com/mujicion/dbus-send.git