Your description does not give us enough information to determine whether the statistical model is correct. For example, how many levels of CASE are there, and how does CASE relate to TRIAL? Are there 3 CASEs with one TRIAL each? Or 3 TRIALs for each CASE? What research question do you have that would be addressed by 12 SCANs in each TRIAL?
Your residual plot and data plot show that there is an upper bound (which is zero) to your response "PlumbResult_0504_LateralDeviatio". Neither the lognormal nor the gamma distribution is appropriate for data with an upper bound; both the lognormal and the gamma have a lower bound at zero and an upper bound of infinity. Both should have failed miserably with a response with negative values (the log of zero is not defined, and I would guess that there was a message to that effect in the log window; always pay attention to the log window).
So, we need to know more about what your response is measuring, in addition to more about your experimental design. Guessing wildly, you might have more luck redefining your response as (-1)*response, if that was sensible in context; that redefined response might follow the exponential distribution, and then the gamma might work (although gamma mixed models can be very persnickety).
Given your current description, I doubt your RANDOM specifications are right but we await more information.
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