Some materials will cause the ink print head nozzle to clog (due to dust generation or the inkjet coating). Once the print head nozzle is clogged, the ink is no longer usable.
If the material has a thin liner, liner cut-throughs are possible, which could lead to media jams and reduced knife blade and wear-strip life.
Please review our Knowledge Base article for more information: What type of labels / media can I use in my LX610 to cut my own shapes?