Validation logic help for multiselect fields

Hi friends,

So, I have something which is driving me kinda crazy. I'm trying to write a validation logic rule where if a particular multiselect field is selected along with any other field that the validation error kicks in.

Here's the formula:IF(ARRAYLENGTH({DE:fieldName})>1&&CONTAINS({DE:fieldName},"option"),"Option must be the only contract selected. Adjust this and resubmit.")

Now, this is a valid expression. However, it isn't validating. I've been trying to cheat with Copilot and Grok and neither are giving me something which works.

This is killing me because there's gotta be something simple that I'm clearly not seeing. 

Help?

-j