Multi select field (Zoho CRM) not pre-populating checkbox (Zoho Forms)

I'm trying to pre-populate a Zoho form with data from our Zoho CRM. I have managed to get all fields to pre-populate except one, and it's doing my nut in :-). Can anyone help?

Here is the URL string:

https://forms.zoho.com/cliiklimited/form/TestingNewPhotographyBrief/?email=test%40testingformfields.com&firstname=Jamesbroome&lastname=test&phone=12345&description=1&numberofproducts=1&angles=1&dimensions=1&imageformat=Full%20Res%20JPEG%3B%20Web-Ready%20JPEG%3B%20PNG%3B%20TIFF&creativelicense=I%20have%20specific%20requirements%20and%20have%20uploaded%20%28or%20emailed%29%20a%20fully%20detailed%20brief%20with%20reference%20images&additionalnotes=notes&companyname=1&tradingname=1&street=1&town=1&city=1&postcode=1&returnproducts=Return%20via%20DPD%20%28at%20cost%2C%20automatically%20added%20to%20invoice%29&returnaddress=Same%20as%20Billing%20Address&insurance=1

It's the Finished Image Format that won;t pre-populate.

I get it to fill out when there is just one option selected, but when customers select multiple options, it doesn't fill out anything. I'm guessing it's got something to do with the de-limiter maybe? currently %3B. Or maybe the format of the two aren't compatible, but I cannot see any other way of getting the same options across both the crm and forms apps.

Any help would be greatly appreciated.