IAR released a new service pack late last week, version 8.50.9.
This service pack includes a new compiler version, which although
thoroughly tested, apparently introduced a new intricate bug, which
causes at least the musca_a mcuboot to fail.
The issue has been identified and fixed, and the next release should
have this fix.
I have no date for when this will be released or in what form.
So for the time being, please do not upgrade above version 8.50.7.
Thanks,
Thomas