App with multiple models, timestamp issue

I have an app with about 12 models, all of which save to my database (MySQL) at UTC, which is what I have my config set to...

config/app.php

'timezone' => 'UTC',

All but one are saving at UTC time, but I have one that saves at local time. It's a Photo model, which has a method that saves photos to AWS-S3. Here's the store method on the associated controller...

PhotosController.php

public function storeSystemPhoto(Request $request, System $system)
    {

      $this->validate($request, [
        'image' => 'required|mimes:jpg,jpeg,png,bmp'
      ]);

      // set the name of the file
      $this->setFileName($system);

      $photo = new Photo([
                  'path'            => $this->destinationFolder,
                  'file_name'       => $this->imageName,
                  'ext'             => $request->file('image')->getClientOriginalExtension(),
                  'caption'         => $request->caption,
                  'photoable_type'  => 'App\System',
                  'photoable_id'    => $system->id,
                  'added_by'        => Auth::id()
              ]);

      // save model
      $photo->save();

      // get instance of file
      $file = $this->getUploadedFile();

      // pass in the file and the model
      $this->saveImageFiles($file, $photo);

      flash('Success!', 'Photo added.');
      return redirect()->route('system_show', ['id' => $system->id]);
    }

I've verified all settings on my server (VPS on Digitalocean) are correct (UTC). I'm not sure where else I'd look to troubleshoot this. Any ideas?