VBA Code to pull data from cell that has data validation

Hello,
I would be super grateful to all who can help me with an issue i am having with one of my macros.
When you open the attached workbook click on 'Open Userform".
Here is a brief explanation of the userfrom:
1) the top right combobox lists all the customers
2) when a customer is selected then if the customer requested a brand then it will list that brand in the "Requested Brands" listbox
3) next, if the a requested brand is selected then the applicable products are highlighted on the "Products" listbox
4) note to consider: the userform is pulling the cell contents of the active customer and the requested brand in order to display the requested products of that brand. the cell contents are stored in a datavalidation list in the cell
5) there are two option buttons, depending on which button is selected the BrandListBox and the ProductListBox are formatted to either act as a "MultiSelect" listbox or a "SingleSelect" listbox, then the user can "AddBrands" to the customer by either adding multiple brands to a single selected product (this will be option button #2) or by adding multiple products to a single selected brand(this will be option button #1).

Now for the issue:
When the first option button is set to true then the user must select a single brand to one or more products and all works well when the "Add Selected Brands & Products" is clicked, but when the 2nd option button is true then the user must select a single product to one or more brands, however, when the "Add Selected Brands..." button is clicked...the code's debugger goes off!

*the code's debugger focuses on reading the datavalidation in the cell and seems that it is having trouble with "storing the previous data validation list into a variable named DataVal".

I have been having issues with this for quite some time trying all possibilities i could think of. I would be truly grateful to anyone who can help me solve this issue.

Thanks in advance

I got rid of some "extra" coding to simplify it, see updated workbook attached to this post.
All you have to do in order to to catch the bug is to open the userform, select any random customer, set the option box on the right to true, select one or more brands and select one product and hit "Add Selected Brands & Products".

Dear Akuini,
Thank you so much for your response.
Thanks for catching that issue and solving it
However, the original issue still stands.
Here is the code that the debugger focuses on, the script marked in red is what the debugger highlighted (please note i've changed a few things around in the code than originally posted but nothing major)
Please note that the below code gets executed only when ProdListBox is set to single-select and BrandListBox is set to multi-select:

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What's interesting to note is that if the cell already has a previous validation list then the code works well for that BrandRow, and if there is no validation then only the first loop works but the rest of the loops (if there is no validation) will bug.