abmet

Yeah the 17-40 wasn’t announced when I purchased mine so didn’t have that decision.  I went with the mk II as I was impressed with what offered and the amount of size reduction they managed. 
 
I saw this that has pretty good comparison between the mk II and the 17-40
https://fujiframe.com/articles/sigma-17-40-vs-16-55-fuji
 

I really like the image quality, size, and weight of my mark II. I never owned the mark I so I can’t help with comparison though it is highly regarded as a great lens.  I don’t use mine for video but I will say it doesn’t have the smoothest zoom, which seems to be common complaint for the mark II.  For photos it doesn’t bother me but I would imagine would be an issue if zooming while recording video. 

I’ve had my X-T5 since launch and usually my missed focus shots are moving and using continuous focus.  I suppose it’s possible I’ve experienced this too but have just assumed I missed the shot or usually it’s lower light shots I notice most missed focus.  It seems like you’ve checked a lot of my thoughts that could be (release priority, AF+MF, face detection on, touch screen focus).  Do you ever half press shutter to recompose?  Could it be you half press and have slight delay before fully pressing?  Wonder if you could rent another lens and see if experience same issues.  I haven’t had my 16-55 mkii that long so I’ll watch for this more closely.  Wish I could help more. 

What aperture and where was the focus point?

Both my X-T5 and X100V display the calculated iso when half press the shutter. Did you happen to change the  shutter AE to off in the button/dial settings?  I think if that is off the iso continues to show max iso when shutter half pressed. 

Glad you figured it out.  Easy to change a setting and forget to change it back, especially when in middle of shooting. 

Do you have a Custom Setting Selected?
https://fujifilm-dsc.com/en/manual/x-t5/menu_shooting/image_quality_setting/#select_custom_setting
If so then you need to edit that custom setting to remove the functions you don't want
https://fujifilm-dsc.com/en/manual/x-t5/menu_shooting/image_quality_setting/#edit-save_custom_setting
As an alternative you can enable Auto Update Custom Setting and then any changes you make will be remembered when the camera is turned off
https://fujifilm-dsc.com/en/manual/x-t5/menu_shooting/image_quality_setting/#auto_update_custom_setting

I haven’t for any of the firmware updates on my X-T5 or X100V and no issues.

Welcome to the forum. Try the Disp/Back button. 
 

I pointed this out a few months ago.
Not sure its greed though - I have no problem with ads as a way of covering costs - but the way its done here just annoys people.

Fixed. Thank you.  The act of adding items to MY MENY activates it, then it is prioritised when you press the MENU button.  I removed all the MY MENU items, which deactivated MY MENU, now the last Menu item is remembered.

I can’t say for sure if will remove it but I’d try a dedicated sensor cleaning kit, or if you have a local shop that does repairs they might offer cleaning services too. 

I can’t say for sure if will remove it but I’d try a dedicated sensor cleaning kit, or if you have a local shop that does repairs they might offer cleaning services too. 

I own all the small primes, love to take them out when I want to travel light and use primes. I bought the 30mm to put it in my bag instead of the 35mm f2. Perfect image quality, great focal length, just in between the 27mm and the 35mm. Use it a lot for images of flowers, small items to show detail, and also documentary work. Certainly not the lens for insects, yet great for all other purposes, and sharp and crisp. My walking around lens is the 23mm, if wider I use the 16mm and if portraits are asked for its the 50mm f2. And for close ups and standard viewing angle its the 30mm. Much more in use than the 35mm, works for me as I expected when I bought it.

What aperture, shutter speed, and iso set too? Is it possible there isn’t enough light?

I have one and like it a lot. It’s a pretty versatile lens. It’s compact and light and autofocus seems pretty fast.  I would note that due to the shorter focal length for 1:1 magnification the working distance is very small. So small that have to remove the lens hood.  For me it’s a great lens but if was looking for dedicated macro lens I’d probably look at longer focal length. 

I understand the site has a need to bring in revenue but the "Advertisement" and "Ad" replies to every forum post are useless and annoying - seeing a possible response to your post and instead being sent to Amazon is just irritating - perhaps the site could switch back to normal ads.

Congrats on the new camera. I agree, I love my X-T5.

It looks the same as mine from what I can tell.  Also looks same as some of the photos I see out there in some reviews.