Overexposed streaks bottom of frame Sony A7 with Manual Lenses

I am using a first-generation Sony A7 with some adapted manual focus OM and M42 lenses with cheaper K&F concept adapters and have noticed overexposed streaks of light along the bottom of the frame of varying size and severity. The effect seems reduced when stopping down and also when shooting in lower light scenarios or in varying angles to strong light sources. I have tried different shutter speeds and turning on and off the electronic first curtain with no consistent ability to remove the issue entirely. I am trying to figure out whether this is due to a light leak with the adapter, reflections off the sensor, or any other possible mechanical issue that I am not thinking of. Has anyone experienced any issues like this, or know of any solutions? I am wondering if a Rayqual, Novoflex, or Metabones adapter would mitigate or eliminate the issue. 


**Update: To update everyone on the issue, the mystery has been solved. The culprit is the shutter. The problem has progressively gotten worse and is now clearly visible with both native and adapted lenses in certain shooting conditions. The problem seems more pronounced at faster shutter speeds. Going back through older photos taken with this camera, with all lenses there were very subtle signs of the issue that were unnoticed upon the first inspection, but now that I am looking for the problem can easily identify it. I still don't know why the issues seemed to be more apparent with adapted lenses, but at least now know what the cause of the problem was, which is a real shame because the shutter still has less than 20,000 actuations.Thank you to everyone for their advice and input. 

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