Modifying the Name-Value pair, ‘MiniBatchSize’, to a lower value can help with this issue. The default value is 128. If a similar issue is present during training, you can similarly set the same property in trainNetwork and imageDatastore to a lower value to help with this issue.
It looks like you are not having license for 'Fixed-Point Designer' toolbox. You can try the trial version of this toolbox by installing it through this link. To get a license for 'Fixed-Point Designer' toolbox, you can contact MathWorks support -https://www.mathworks.com/support.html
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