Unable to achieve Cmax

Dear All, I am a Beginner for NONMEM. I am having a dataset of oral BE study. The Drug is BCS III and tmax is 0.5-2hrs. I have observed lag time and double peak; but I am not assure it is double peak or sampling error. I have used ALAG in the control file to deal with lag time. The half of the subjects are following 1 compartmental absorption and the rest are following 2 compartmental absorption. So I separately modeling each compartment. Is it right method?? Should I use transit model? The elimination phase is captured well; but I am unable to achieve Maximum Concentration. The CWRES vs. Time & CWRES vs.PRED plots clearly indicates bias at high concentration. Please suggest me some needful actions to deal with these problems. Best Regards Anuja "Disclaimer: Legally privileged confidential information, binding only if confirmed in writing by a person authorized by Cipla. Please notify sender immediately and permanently delete message if you are not intended recipient. This email is an informal communication and not a definitive opinion of the company or the author. Thoughts or ideas expressed here may be incomplete or in error and subject to further review and change. Thank you."