Some DPs from past promos and the Freedom's 5x bonus categories seem to suggest that if you make a return, Chase will claw back only 1x UR of the value from the transaction, leaving you with 9x UR for the Chase Pay promo (or 4x UR in the case of 5x bonus categories). With how wonky Chase's IT has been with properly awarding UR points, I wouldn't chance it.
Assuming you're still in the return & exchange period, what you could do is either (1) ask for a price adjustment using the coupon; or if the price adjustment will take you under the $300 limit that maximizes the deal then (2) don't ask for a return/refund -- ask to
exchange your item for a
Best Buy gift card. The second option will not put any charge back to your Chase card so you don't have to worry about any returns or claw backs. You get equal dollar value on the Best Buy gift card, which you can use with your coupon to repurchase your item. Whatever is left, you can use towards a future purchase, or *fingers crossed* still use for a third-party gift card.