This issue usually arises in workflows that utilize ControlNet.

It's highly likely due to not using a unified base model file. For instance, if the Checkpoint is using a base model that is sd1.5, whereas the ControlNet node is using SDXL.

To resolve this issue, use a unified base model file. For example, in the scenario mentioned above, you can replace the model file in the Checkpoint with SDXL.
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