spi_transceive blocks indefinitely at spi_context_wait_for_completion

I've created a new sandbox project for a nRF9160DK that requires a SPI Master for testing a Flash part. Since I already have "working" SPIM code in a different Segger project, I just copied that code to the new project. Unfortunately, when I run the new project, it just hangs at the spi_context_wait_for_completion() call at line 241 in the spi_nrfx_spim.c source file (see attached screenshot). I copied over the same C-source file, prj.conf file and nrf9160dk_nrf9160_ns.overlay file that I use in my other project. And that project is working perfectly. So I'm surprised that one project works and the other doesn't with almost identical code. I have read several topics of developers reporting the same blocking condition, but I'm not seeing any solutions. 

I have attached the prj.conf and overlay file and a screenshot. Please let me know what else I can check. I'm sure it must be a config issue as my SPIM code is identical in both projects.