I know this is not solving the problem with Gallery but may I recommend a new approach.
Save all your photos to Google Photos. Use Google photos to create Albums and tag faces and all that. This will remove your dependency on your phone and allows you to quickly be able to switch to another phone without any worry about your photos getting lost and will allow you to view your photos on Computer too (same Album structure and all). Then additionally if you ever use Chromecast device with your TV, you can have your photos as Slideshow.
On Saving Photos to Google: You have the option to save photos in Standard Res (unlimited Storage) or High Res (5gb free and then you need to buy space from Goog). Depending on how you do it, you may then want to remove the original photo from your phone or keep them on your phone and when the phone storage is filled download them all to a PC for safe keeping.
You can set that all your photos are uploaded with Privacy set to only be visible by you. You can create albums and Google creates Albums for you from Events too (you can turn that off). It is pretty cool.
All these settings are in Google Photos App.
That happened to me also after doing the update NEVER AGAIN! anyway I took some advice here to clear cache... that deleted 194 photos from my phone NEVER AGAIN. THEN I called Samsung and this is what they told me to do: It worked btw.
Go to settings
Go to about phone
Tap build number 7 times (this turns developer options on)
Go to developer options then USB configuration
Select PTP (picture transfer protocol)