Sheets: Cannot read property 'toString' of undefined(latest Version)

I am trrying to lookup a row in a sheet but get the above error on random inputs.
This is very weird as everything else is fine and this error is random for some inputs.

Please help!

Welcome to the community @Rahul_Purohit!

Is it possible that you have multiple incoming items and for some of them there is data missing and the expression you have set on Lookup Value does so resolve to undefined?