I've had my 2014 in 4 times on check engine light. Showing exhaust system codes. They went through entire DEF system and finally found crystals in or near DEF injector. Replaced injector. Only made it 40 miles before Ck engine is back on. Headed back to dealer this week. Started all this at maybe 3000 miles. 7400 miles now. Thoughts? Others experiencing this?