Hmm, can you provide screenshots of your tables as well as the formula you're using that's giving you an error please?
I'm able to multiply a lookup of a currency field like so:

Hmm, can you provide screenshots of your tables as well as the formula you're using that's giving you an error please?
I'm able to multiply a lookup of a currency field like so:

Hi @TheTimeSavingCo Adam, thanks for looking into this!
Sharing is a bit difficult, because there are confidential names in there 😊 But here is a formula causing NaN errors. (I blurred out a name in the screenshot)
2 fields with valuta and the 3rd one is Lookup field with valuta.
Hi @TheTimeSavingCo Adam, thanks for looking into this!
Sharing is a bit difficult, because there are confidential names in there 😊 But here is a formula causing NaN errors. (I blurred out a name in the screenshot)
2 fields with valuta and the 3rd one is Lookup field with valuta.
Hm, summing a lookup and two currency fields works fine too:

Without a screenshot it's pretty hard to troubleshoot as I'm pretty much guessing what your setup is and what could be causing the issue I'm afraid, sorry! Perhaps you could recreate the issue on another base or something?