K1. Live view and flash.

Just back from a visit to a local studio and I had a very odd and frustrating time.

The best way to work was to use live view with the camera on a tripod, looking down onto the tilted screen. I take the studio's trigger, press the test button, flash fires, fit to to my camera, click the DOF preview test no flash. I know if the shutter speed is too fast it won't fire, this is Manual with a speed of 1/60th  or X mode so it's not that.  
We try alternate triggers. Same thing. I've used this studio before and triggers are the same ones which worked before. It's nuts. 
Maybe the two triggers we're using don't like the Pentax electronics, I have a PC socket to simple hot shoe adapter in my bag. We try that with the triggers. No joy, we find a PC socket to 1/4" connector cable, I can short it and trigger the flash, but plug it into the camera no flash.   What the actual ...  ?

Somewhere the camera turns off. When it comes back on NOT in LV  the flash fires. and keeps firing. Put the wireless trigger back on. Flash fires.  Fine I'll get down on the floor and look through the OVF. Get to the end of the session I'm wondering is it Electronic shutter, or something else rather than LV generally, and now I can't repro the problem at all.  What the ... ?

Has anyone else got any experience with this ?

My K1 is set for electronic shutter in Live view and if I am in P / Av / Tv / TAv / Sv or M mode when I go to live view the [ES] icon appears at the top of the display. If I am in X mode when I go to LV the [ES] does not appear.

The original manual doesn't mention the Page 2 option of LV electronic shutter mode it is described here.  https://www.ricoh-imaging.co.jp/english/support/digital/pdf/K-1_Ver.1.30_Detail_for_Enhanced_features.pdf  and it says

*The drive mode that can be used with Electronic Shutter are single frame
shooting, Self-timer shooting (12s/2s), Remote Control shooting (immediate / 3s),
Mirror up shooting and Multiple exposure.
*The Shake Reduction function is fixed to OFF.
*The external flash is fixed to off (will not discharge)

I have a feeling that changing mode to X when already in LV and going into LV when X is selected give different results.

My 1st thought is that the readout speed in electronic shutter mode is too slow for allowing useful work with flash. And that could be the reason that Pentax disabled flash altogether in ES. That also explains why SR is disabled.

It's been a while since I used my K-1, but can you set to mechanical shutter in LV?

Sjak wrote:

My 1st thought is that the readout speed in electronic shutter mode is too slow for allowing useful work with flash. And that could be the reason that Pentax disabled flash altogether in ES. That also explains why SR is disabled.

It's been a while since I used my K-1, but can you set to mechanical shutter in LV?

That theory is quite possible. The release note suggests there is a a rolling shutter effect so there may be no "sync speed" that works The ES is turned on or off in on page 2 of the camera menu. I think I switched it on a while ago and it's not the good idea I thought it was.