Usually the thread concurrency is to blame.
Note: In case you havent set this up in the command prompt first. Please go start -> run -> type "cmd" -> press enter. Than type: setx GPU_MAX_ALLOC_PERCENT 100 and press enter.
Than try these specs.
--thread_concurrency 21712 or 16834
--gpu-engine 1100
--gpu-memclock 1500
If one thread conc doesnt work, than try the other. GL
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