That is odd, there are very few other settings that limit using es. Having a flash unit attached is one, but I would have thought that would also keep you from using ms+es.
Mines does this:
Have you upgraded to the most recent firmware?
This may sound drastic, have you copied you settings down somewhere and tried a full reset?
I agree with all that's been said above, hence my decision to buy XS10 rather than XT4. The reputation of Pentax was that if it got covered in mud you could wash it under a running tap. I never tried that but was happy to use it in briefly in heavy rain and desert sandstorms and never had a problem. I wouldn't be that confident in such circumstances without weather sealing and would use poly bag and chamois even in less extreme conditions.
It's often the small doors covering SD slots, batteries etc that aren't sealed, and some times cable and microphone or remote shutter sockets have no cover at all. Sealing a pop-up flash isn't easy either. Worth protecting those points if you're out in weather you want to protect yourself from.
Scroll down to Shutter Type.
It is in the shooting menus setup, you can choose between manual shutter, electronic shutter or both together.
I have been trying to use my x-t30 with the electronic shutter but not having much success As it's a mirrorless camera I thought it would be straightforward! But there appears to be no way to manually select it (only combined ms/es). I've set it to auto with 1/125s exposure. I'm using a hand-held wired shutter release. I'm sure it was working before I updated the firmware to 1.40 a while back but I confess I haven't really used it since. Am I missing something or is there any way around this issue? At the same time, I can take short video clip and it's fine - surely I must be able to take a still?
Thanks for any suggestions