Problems and Complications with Lumineers?

The answer is simple.  Avoid Lumineers if possible!  The porcelain is of poor quality.  The Lumineer people recommend finishing the edges at the gum line of the Lumineer with a dental bur (drill) which is an absolute no no with veneers.  Often the Lumineers are overcontoured which can cause chronic gum inflamation. 

When Lumineers or any restoration are placed properly most of the complications listed should not be experienced. The reason for #1: Halitosis- may be due to: poor seal on the restorations which allows bacteria to gather at the margins of the restoration and can create Halitosis (bad breath); #2- Breaks or cracks: can be due to improper bonding or an inaccurate bite. The breaks can also be due to a patient that is grinding his/her teeth and not wearing a Nightguard to protect the restorations; #3- Gum disease: Can be due to the improper placement of the restorations causing irritation of the gums. This could be because the restorations were placed too deep into the tissue. When restorations are placed above the gums, they allow for better tissue healing and a healthier more cosmetic appearance.Good luck!

Lumineers is touted as "no prep" veneers. If there is no margin (recessed edge), then there will be a ledge at the edges. This can trap plaque, which can smell or stain. Trapped plaque can also lead to gum disease. Bulky edges can irritate gum tissues, leading to gum disease.
Since they are very thin, they are more prone to break.
Not all Lumineers cases are terrible, but often these cases disappoint people and get replaced.