If you're getting an error with the sampled pads in Sunday Keys Version 2 in MainStage, make sure you are saving copies of the Sunday Keys 2 concert in the Sunday Keys 2 folder and that you've gone through all installation steps in the installation videos over on the Sunday Keys Resource Page.
The missing .exs instruments are related to the custom sampled patches in Sunday Keys Version 2. Those samples are saved to the original Sunday Keys concert, so opening the patches that resource those custom samples in a different concert could be causing those errors. There is a video on the Sunday Keys Resource Page that covers how to reduce the size of the Sunday Keys concert, this will also cover how to save those custom samples to your hard drive so other MainStage concerts can find them.
We had somebody recently describe that the EXS plugin had trouble finding the custom samples and when that happened it would just jump to load a different preset. Following the steps in the “Reduce the size of you concert” video seemed to solve the issue. You’ll find this video towards the bottom of the Troubleshooting section on the Sunday Keys Resource Page The custom sampled patches are the Altar Call Pad, the Wonderful Pad, and the Worship Pad. I would check patches that contain those sounds to see if they are the only ones causing the trouble, if so then it should be easy to fix.
Two other things to check:
1. Make sure these boxes are checked when you "save as” from the Sunday Keys concert
2. The .exs files and samples are saved into the concert, confirm that they are there by right clicking the concert, show package contents, Sampler Instruments: