I have a EHWIC-4G-LTE-G running firmware SWI9200X_03.05.19.04ap, which I am not able to upgrade.
The release notes for the latest version of firmware says there is a two step upgrade, first needing to upgrade to 03.05.24.00A, before 03.05.29.02.
Also the following doc suggests if running < 3.5.24 you should first upgrade while running 15.2(4)M2:
I have tried upgrading to 03.05.24.00A while running 15.2(4)M2, and get the following messages in the log:
Did you get it working. I am having a similar issue upgrading from 3.5.19 to 3.5.24 (as the release notes for 3.5.29 recommends), on a 15.5 IOS version.