Nexus 7 (2013) lost root on 5.0.2 flashing SuperSU don't help topic

My N7 has a unlocked boot loader, and I have been using CWM ever sense I got it. I have had several ROM's installed and always had root. When I received 5.0.2 I lost my root access, and now it is running extremely slow, do to a tons of games my son have installed. I can't control autostart without root, and yesterday, I tried flashing and rooting, I both tried with TWM and CWM, and I installed superSU from boot loader, without any errors. But still I don't have su binaries installed. Also when I install boot loader it only works doing installation.

Please advice what you try next

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