My EM1 Getting Derailed

[Melwin]

Hi all.. I bought my Bachmann EM1 2-8-8-4. I just made my first track layp-up using flexi track and the EZ track. My diesel runs well with not much issues but I am having issues with my EM1. When I try to run ahead, the front 2 wheels seem to run out of rail and then followed by the next 4. The front tend to lift as I push the throttle ahead. It was running fine for few runs then the problem started. I finally had to run my EM1 on reverse.
I am still trying to figure out why the front tend to get lifted. I hope I can get this sorted.
I am new in this hobby, so I do hope some advise from you guys.

[brokemoto]

Purchase a gauge and make sure that the pilot wheels are in gauge.