CDBC

Well to begin with, are your viewfinder settings identical, for brightness and white balance etc? Have you set up both cameras, on all the same settings, so as to make an identical simultaneous photo of something? Because otherwise, everything is subjective. I used Canon for decades, and loved their equipment. But Fujifilm have had me in their grasp for twenty years now ...

No idea, but 4.32 is, I think, the latest software update.

A new update reminder (4.32) just showed up in my email inbox this morning, may be worth checking that out.

What Chas said. It's impossible to objectively determine how 'sharp' a lens is while you're shooting hand held. I don't think even a monopod was used to take those pictures. Even if a photographer doesn't have a proper chart, objective assessments can be made taking pictures of a brick wall (including barrel/pincushion distortion found in some zoom lenses).

What further upgrades do you think the X-T2 requires?

My X-T2 doesn't 'work' that way. If the On/Off switch is turned on, that will illuminate the screens just fine, but then the initial touch of the button only triggers the camera to focus and set its' exposure. I have to push further to make the trigger go off. Quite controllable, to my mind. I just tried this with my camera settings the same as yours (Single shot, Averaging metering), so I suspect there may be something in your various settings that may be triggering this (forgive the pun). Hope you're able to figure things out, or it may be time to send it to Fuji for a quick repair; I would suggest that you send that video you made to your local distributor and see how they respond. Best of luck!

I think you mean sensitive ...

This thread here may have the answers you're looking for.

Are you shooting with the lens at full aperture? Put that camera on a tripod - heck, you're shooting what is effectively a 600 mm (which I think would be a 900 mm equivalent in 35 mm terms), so trying to hand hold the camera isn't likely to work very well anyway. Those stationary seagulls don't need 1000th of a second, but lenses generally produce a crisper image when stopped down a bit.

Looks normal to me, given the wide aperture and near focus point.

No, it's a digital camera. They're all complicated and fiddley - even the point-and-shoot type. Sometimes, I get the feeling that in the film era the choices were much simpler, and the camera was - at least potentially - a tool designed to help the photographer realize his/her vision. But in the modern era, it's as though the designers don't even actually take photographs themselves, but feel compelled to produce the device with the most menus, buttons, and choices - regardless of whether they are of practical application in assisting the photographer.

Why don't you try going into a real camera store, and try the actual Fujifilm flash on your Fujifilm camera? If it works, then you know the problem isn't the camera. So far as compatibility is concerned, it was around 1976 (the era of the Canon AE1) that simple hot shoes (negative contact through the sides, positive contact through the single point in the middle of the shoe) became a thing of the past. Meanwhile, your X-T2 has five (5!) additional contacts in the shoe; I'm guessing that some of them actually have a purpose.

Just a random thought; but if there's an intermittent electrical glitch it might be worth considering whether the camera was under heavy use (creating a fair amount of heat) when the problem occurred. If there is such an association then it would make sense that you can't reproduce it easily. On the bright side of things, should my guess be correct, then with two X-T2 bodies in your possession then maybe you could work around it instead of throwing money at it?

Are you using genuine Fujifilm batteries?

Couldn't agree more. Equivalent to a 35 mm lens on a 35 mm camera, with that 63 degree angle of view, so more universally useful. Plus, apart from the excellent specifications, it's pretty lightweight and compact. If I only had prime lens to go out and shoot with, this would totally be my choice.