var imageProcessorBuilder = new ImageProcessor.Builder();
var imageProcessor = GetObject<ImageProcessor>
(imageProcessorBuilder.JniPeerMembers.InstanceMethods.InvokeVirtualObjectMethod("build.()Lorg/tensorflow/lite/support/common/SequentialProcessor;", imageProcessorBuilder, null).Handle, JniHandleOwnership.TransferLocalRef);
This is still a problem even with the very latest versions and it seems to affect not just the ImageProccessor.Builder but other Builders too (like TensorProcessor.Builder)
Try this