Inconsistent Exposure with Canon R8 and flash photography

[Alamond]

Hello, 

I recently purchased a Canon R8 to replace my old Canon 550D. 

Currently, I'm having a problem with inconsistent picture exposure taken by the R8 with Godox trigger and speed lights. Sometimes a picture is the perfect exposure, and other times its overexposed. Happens randomly. I'm using the same equipment as I did before and never had this issue with the 550D. 

Current Setup: 

• Canon R8 Camera
• Cannon EF 100mm f/2.8 Macro lens
• Meike MK-EFTR lens Adapter
• Godox XT1-C trigger
• 3 Godox T600 speedlights

Settings I'm using:

• Manual Mode on both the camera and flash trigger 
• Shutter speed 1/200
• Aperture: F11
• ISO: 100

Any help will be much appreciated. 

[kvbarkley]

Do you have a flash exposure meter to verify the output of the flash?

Does the EXIF data verify your manual settings?

[Alamond]

I don't have a flash exposure meter. 

And, the EXIF data of the picture file is showing my manual settings. 

edited to answer both questions. 

[deebatman316]

@Alamond Godox flash products are NOT fully compatible with Canon cameras. The EOS R8 does have some incompatibilities with Godox flash products. The EOS R8 doesn’t have a full mechanical shutter such as the EOS R5 Mark II. It uses an electronic first curtain with a mechanical shutter for the 2nd curtain. Undesirable effects may be seen such as banding. Also 3rd Party Mount adapters cause all sorts of problems to the point. Canon forced 3rd Party companies to pull their Mount adapters due to such problems. The lens aperture may NOT always be stopping down causing overexposed pictures. Let’s troubleshoot without flash first and see if the problem returns. Adding a flash much less multiple off camera flashes adds complexity to the problem. Also can you share pictures with us. Preferable through a file sharing service like Google Drive. With EXIF/ Metadata intact too. 

[Alamond]

Update: 
Problem solved following these tips I found online:
1- Godox XT1-C trigger was updated to the latest version (v.27 at the time of this post)

2- New EOS models like the EOS R8 has a different hot-shoe design that the old DSLR I used. When Inserting a trigger like the I used, it must kept in mind. When inserting you have to either push a little bit forward or pull a little backward until a click is heard (5 pins on the hotshoe faces the ones on the trigger) and then lock the trigger into place.