Connecting CDJ 900 with CDJ2000

Hello. I have recently bought a pair of CDJ 900s and was super happy to add them to my existing setup of 2 CDJ 2000nxs and my xone 42 but I do have quite strange issues. CDJ 900s do not read bpm correctly since they drift apart with tracks played on cdjs 2000nxs. I am aware that bpm of cdj 900 has no decimal and I am used to that but the reason over here is of a different nature if I adjust bpm on cdj 900 just by ear and make it sync with 2000nxs then bpm difference is quite significant. Was looking for a firmware update but firmware is newest one. Firmware on my cdj2000nxs is also newest. Also one of my CDJ900 does not allow me to create loop manually, if I start a loop with loop in button it blinks 4 times and goes off and my loop out button does not react. I hope this issue can be solved with your help. Thank you.