CTW MX-2 with wide range of FPS

Good afternoon,

Have a CTW MX-2 which presents a problem.
She is chewing BBs and has a wide range of FPS.
Sometimes it does 90fps as the next shot is 250 or 340fps, with CS350 cylinder.
Where should I look to my attention?

regards,

i heard ppl with the same issue

apparently the mag doesnt feed fast enough with the lower power springs, read this:
https://celcius-ctw.forumotion.com/t334-bbs-chopping-going-25-ft-other-questions