Mbed-os-example-lorawan with Seeed Lora E5

Using mbed-os-example-lorawan, mbed 6 (master) in mbed studio.

The mbed lorawan example works fine with the MTT Xdot STM32L, but I cannot get it to work with the STM32WLE5 based Seeed Lora E5. It tries to join, Tx is OK, but then it hangs and never switches to Rx. I also find that it hangs if I use rtos::ThisThread::sleep_for( ). I mention this observation because I suppose there may be a common cause.

I’m struggling.

I’ve tried a few more things and find that sleep_for() does not hang with a debug build profile, however it then crashes during the LoRa join process.
I suspect the problem might be in the clock config since similar problems have been reported using other STM MCUs in mbed 6 but I have not yet been able to make progress there.