How to apply u-blox SARA-R410M CIoT module 05.08 FW update to MKR1500?

Hi,
does anyone know how a new u-blox SARA-R410M CIoT module FW release can be applied to the MKR1500 board? Following the u-blox EasyFlash steps with the correct FW 05.08 file available and running the MKR1500 in a pure serial pass-through program mode does not appear to work. EasyFlash (from u-blox) requires that the device be powered up after it is waiting to re-flash the SARA-R410M, but doing this results in a time-out "device not found" error in EasyFlash.

How is a SARA-R410 module FW update supposed to be applied to the MKR1500?

The new 05.08 FW release has many bug fixes and new features, so it is quite important to try to apply.