Thoughts On This 50-150S image

Maybe I should post this elsewhere.  I'm open to suggestions.

• Image below was shot with an NX1 and a 50-150S lens.
• No cropping or PP prior to full size export from LR
• Lens was set to manual focus (peaked onto windmills)
• Lens OIS was turned OFF
• Camera was mounted on Manfrotto tripod (forget the model but it's a mid-range model) and using the lens mount point [as opposed to the body mount point].
• No wind at all
• several seconds were allowed to elapse after focus and no longer touching the camera before pressing cable release button
• Cable shutter release was used
• Image posted is the 0 EV of a 5 bracket (1.7 ev) raw capture [with EC left at 0]

I captured a number of similar images of the same scene at different focal lengths and compositions, and of about 6 bracket sets, only one came out useable [if not pixel peeping].

This image (viewed at 100%) is representative of most of the "bad images" where movement is noticeable in most of the scene and especially with looking at the horizon and the wind generators in the far distance.

I rarely use this 50-150s lens. I usually use the 16-50s. I am very pleased with the overall performance of the 16-50s combined with the NX1

Questions ...

• Is this possible internal movement from previous shutter mechanical movement?
• Do I need to weigh down my tripod even with no wind?
• If I had left OIS on, would image have been better or worse in terms of movement?
• Maybe an issue with the lens?
• I'm not too thrilled with the LENS mount location/balance on the NX1/50-150s setup. Would BODY mount maybe have been better?
• Just too far? (if so, would a better tripod setup probably have helped to an extent?)
• Maybe the slightest movement of the attached, handheld cable release is responsible? I make it a habit to be completely steady even when shooting this way and never make contact with the assembly as long as there is no wind as was the case here. (Seems to be up/down movement only)
• Am I expecting too much?

View windmills on horizon at 100%

I realize this is a long shoot, but somehow I expected better.

Thanks.