If you’re a swiss tax resident, and your polish broker continues to consider you as being taxed on Poland maybe close your account and switch to some other broker (e.g. IBKR).
Poland - Corporate - Withholding taxes has a 19% withholding tax on dividend.
I assume you’d need extra paperwork to benefit from the 15% treaty rate between Poland/Switzerland, and not sure if IBKR will provide it:
the domestic WHT rates can be decreased by a DTT concluded between Poland and the payment recipient’s country of residence if certain administrative conditions are met (i.e. the payer obtains a valid certificate of a fiscal residence of the payment recipient/beneficial owner).
This means that you would only get 15% back on your DA-1 and 4% are likely not recoverable (if you can’t do the paperwork).
(still better than the current situation where your broker treats you as a polish tax resident)
edit: Capital gains in Poland - Swiss tax residency for a previous discussion