LastName not saving on Create Update CRM Customer action

Hi. First up, I am very impressed with what I see from Zoho Flow. It is exactly what we need to connect cloud services.

However, I have a strange error occurring.

I have created a Zoho form which collects first and last name and email, along with some other data.

I have created a trigger for when a new form is created, which works perfectly.

The trigger then passes to a Create or Update Contact (ZohoCRM integration).

I can configure this create or update action alomst perfectly - the first name, email and all other data from the webform can inserted as fields into the Create or Update action.

HOWEVER, the mandatory LastName field of the Create or Update action will not retain ANY information I place in it. Not the LastName field from the form, or even a static test text. Whenever I save the Create or Update action, and then return to it, the LastName has been set to blank.

As a result, every attempt to run this flow results in a failure.

To be clear. The LastName field of the ZohoCRM Create or Update Contact action refuses to store any data upon being saved.

Any help you can provide would be useful, as I plan to use the Create or Update function a LOT in the future. It is probably the single most important integration for this tool.