Every POD platform runs its content review the same way. A rights owner searches for their name, reports the listing, the platform removes it and counts a strike against you. Three strikes on Merch by Amazon and the account is gone. Nobody at the platform checks whether the complaint was fair before acting.
So the question is not whether your design infringes. It is whether the words on it match a live mark that someone is willing to enforce.
The five categories that cause most strikes
Sports teams and leagues. Team names, nicknames, city plus team combinations, even the phrase "Big Game" around the Super Bowl. The leagues enforce hard and often.
Characters and franchises. Names, catchphrases, and anything a fan would recognise. Owners of animated franchises are the most active reporters on Etsy by a wide margin.
Common sayings that someone registered. This is the category that surprises sellers. A phrase you have heard your whole life can be a registered mark for t-shirts. The owner does not need to have invented it, only to have registered it first for that class.
Single distinctive words. "Onesie" is a registered mark in several countries. So is "Yeti" for drinkware. So are a surprising number of ordinary-looking words in class 25.
Brand names used as adjectives. "Nike style", "Disney inspired", "Yeti compatible". On POD there is nothing to be compatible with, so these phrases read as trading on the name.
Check the text, not the design
Paste the exact words from your design into the checker above. Choose Merch or Etsy so the classes are set to apparel, mugs and bags. Anything that comes back as a live mark in those classes with a high score is a phrase to replace, not to tweak.
I do this for every phrase before uploading, including the ones that feel too generic to be anyone's. Those are exactly the ones that turn out to be registered.
If you already have a strike
Read the notice for the specific mark cited, then look it up. If the mark is dead, in a different class, or the complaint cites a phrase your design does not contain, a counter-notice with the register printout often works. If the mark is live in class 25 and your design uses it, remove the design everywhere, not just on the platform that complained. Owners check the others next.