Created attachment 145262 [details]
the problem

I experienced this only a windows 10 64-bit version machine (but NOT on dev version compiled on debian jessie machine).
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Libreoffice About:
Verzió: 6.1.2.1 (x64)
Build az.: 65905a128db06ba48db947242809d14d3f9a93fe
CPU szálak: 4; OS: Windows 10.0; Felületmegjelenítés: GL; 
Területi beállítások: hu-HU (hu_HU); Calc: group threaded
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Graphics:
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Display Devices
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           Card name: NVIDIA GeForce GTX 950
        Manufacturer: NVIDIA
           Chip type: GeForce GTX 950
            DAC type: Integrated RAMDAC
         Device Type: Full Device (POST)
          Device Key: Enum\PCI\VEN_10DE&DEV_1402&SUBSYS_36C31458&REV_A1
       Device Status: 0180200A [DN_DRIVER_LOADED|DN_STARTED|DN_DISABLEABLE|DN_NT_ENUMERATOR|DN_NT_DRIVER] 
 Device Problem Code: No Problem
 Driver Problem Code: Unknown
      Display Memory: 6066 MB
    Dedicated Memory: 2007 MB
       Shared Memory: 4059 MB
        Current Mode: 1920 x 1080 (32 bit) (60Hz)
         HDR Support: Not Supported
    Display Topology: Internal
 Display Color Space: DXGI_COLOR_SPACE_RGB_FULL_G22_NONE_P709
     Color Primaries: Red(0.635266,0.349133), Green(0.332531,0.619641), Blue(0.155773,0.055188), White Point(0.313000,0.329602)
   Display Luminance: Min Luminance = 0.500000, Max Luminance = 270.000000, MaxFullFrameLuminance = 270.000000
        Monitor Name: Generic PnP Monitor
       Monitor Model: S22C200
          Monitor Id: SAM09B7
         Native Mode: 1920 x 1080(p) (60.000Hz)
         Output Type: DVI
Monitor Capabilities: HDR Not Supported
Display Pixel Format: DISPLAYCONFIG_PIXELFORMAT_32BPP
      Advanced Color: Not Supported
         Driver Name: C:\WINDOWS\System32\DriverStore\FileRepository\nv_dispi.inf_amd64_52ac7eb8f32780d5\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_dispi.inf_amd64_52ac7eb8f32780d5\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_dispi.inf_amd64_52ac7eb8f32780d5\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_dispi.inf_amd64_52ac7eb8f32780d5\nvldumdx.dll
 Driver File Version: 24.21.0013.9882 (English)
      Driver Version: 24.21.13.9882
         DDI Version: 12
      Feature Levels: 12_1,12_0,11_1,11_0,10_1,10_0,9_3,9_2,9_1
        Driver Model: WDDM 2.4
 Graphics Preemption: DMA
  Compute Preemption: DMA
            Miracast: Not Supported
 Hybrid Graphics GPU: Not Supported
      Power P-states: Not Supported
      Virtualization: Paravirtualization 
          Block List: No Blocks
  Catalog Attributes: Universal:False Declarative:False 
   Driver Attributes: Final Retail
    Driver Date/Size: 2018. 07. 30. 2:00:00, 952696 bytes
         WHQL Logo'd: Yes
     WHQL Date Stamp: Unknown
   Device Identifier: {D7B71E3E-5742-11CF-7251-CE161BC2D535}
           Vendor ID: 0x10DE
           Device ID: 0x1402
           SubSys ID: 0x36C31458
         Revision ID: 0x00A1
  Driver Strong Name: oem6.inf:0f066de3d2378488:Section076:24.21.13.9882:pci\ven_10de&dev_1402
      Rank Of Driver: 00D12001
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I don't know if it is related to the windows presentation subsystem or to the pdf generation, but here are the steps I did for reproduce the issue I have experienced after importing from pdf, maybe the image preview was used for flipping, not the original page:


1) I copied the image from the problematic document to the new one, this is now slide 2.
2) I duplicated the slide as slide 1 and applied vertical flip.
3) I duplicated the slide 2 to create slide 3, applied vertical flip and convert to metafile.
4) Convert the document to pdf and check if it is broken (yes, the slide 1).