AHey CC Family

Just a quick post to see if anyone has experienced this problem. The last three cakes I made from the Duncan Hines Classic Yellow has baked up with a hard crust/shell on top of it! The cake underneath is sometimes cooked and sometimes not! It is so strange! I have calibrated my oven, used room temp ingredients, used WASC, everything I could think of. But still the same problem.

My question is has anyone experience this problem and if so how did you correct the problem?

Any advice and/or suggestions would be greatly appreciated!

Thanks!!!!