If you materially alter the item, in a way that would surprise the consumer expecting an item with that trademark, it can be a problem. The example legal eagle

If you materially alter the item, in a way that would surprise the consumer expecting an item with that trademark, it can be a problem. The example legal eagle on youtube gives is a sunglass manufacturer with special protective lenses. A reseller replaced the lenses, and a customer would be expecting the special lenses when they bought them with that trademark. So the court decided that change was material and found against the reseller.