eCart cannot be the last extension installed.
when you uninstall eCart 5.0.3, you will need to also uninstall either Design Extender or Data Bridge, doesn't matter which one, then reinstall eCart 5.0.4, followed by whichever of the consolidation projects you removed.
I have logged a bug in regards to the Units Select lists, we will be releasing updates to both Design Extender and Data bridge to correct these issues that are surfacing.