Flash not working on R5

I think the problem is that the triggers and not communicating with the camera precisely enough. I've got a the Canon R5 with a yongnuo trigger. It pops the yongnuo speedlight which in turn causes the Bowens main light to see the speedlight and respond by flashing.

I was doing a model shoot and moved my Bowen's light for the next setup. All I did was move it a few feet over. I changed nothing else. The yongnuo was used as a hair/rim light behind and above the model. Suddenly, all I'm getting is the hair light but the main light is not showing up in the images! That means the shutter is closing after the speedlight but before the main light responds. So there's a couple of options on issues:

A) The timing is slightly off on the communication between trigger and camera and its just not quite staying open long enough.

B) The shutter is malfunctioning and not staying open as long as it should.

I'm thinking its probably the trigger because I was starting to have shutter problems with my old 5D Mk IV, which was why I got the R5. I only had about 100,000 actuations on it and it should be good for 125,000 to 150,000. But I figured it was several years old and was just growing weary. Here's the thing though.... I don't know at what exact point I started having the shutter issues on the 5D, but it so happens that I was out on a shoot in the park and my trigger somehow got loose and as I was walking, it fell off. I only realized it because I stepped on something... the trigger! It was fully dusted with dirt and a bit scratched up. I think I recall that it stopped working and I finished the shoot with natural light. I immediately ordered a replacement trigger - the same one.

What I'm wondering now is did my 5D really have a shutter issue, or was it the miscommunication between the new trigger and the old camera, which is now causing the same shutter issues with the new R5? The timing just might be slightly enough off that I catch that bit of shadow on the right side of the vertical images.

Being an intermittent issue, its not like I can do any testing. In a 200 image shoot, it might happen 3-10 times, so I can't take a shot, adjust something, take a shot and eventually eliminate all the possibilities.

It is interesting that the Bowens wasn't showing up - that second flash that responds to the first can be that fraction of a second difference that just misses the timing.

Now that I've got a big suspicion that its trigger related, I'll just have to keep shooting and try to confirm when its happening. If my theory is correct, when I'm doing my headshot sessions I use constant LED lights, so there's no flash - well, not when I work with my black background. I do flash the white background to brighten it and I do know for a fact that I occasionally do have a big shadow on the bottom from the shutter on some of the shots. But there again, we could be talking trigger. If the shutter shadow happens when I'm not using flash, then its definitely the shutter. If it doesn't happen, then it must be the trigger. Now I know what parameters to look at when/if it happens again.

As an aside, I gave up on the R5 at that shoot and grabbed the 5D to finish the session. I may have had another frame with the shutter issue, but it was all dark and I think the flash just didn't fire at all. I hated working with the 5D because now I'm so used to the R5 that I kept going for the wrong buttons. In frustration, I picked up the R5 again, and then it functioned perfectly fine the rest of the shoot! I figured, still thinking it was the camera, that it had time to rest and something needed to reset itself. But now I'm thinking that maybe the trigger was a little loose and that when I switched it back and forth between the cameras, it was being tightened each time, so communication was good. I will say that I have noticed that that trigger comes loose a lot. The old one stayed tighter longer. So this could all be as simple as making sure your contacts are clean and your trigger is snugly mounted.