Mesh with archer c7 v5

hello folks,
i built mesh network with my archer c7 v5 and belkin RT3200. in bgn mode, it work perfectly but in ac mode i have very low bandwidth (20 Mbps download and 170 Mbps upload). Is there any solution to have correct flow, otherwise if there is no solution (the problem is from archer c7 v5, i have done some research and test with another mesh node) wich device pricing average 50 € i can use replacement my archer (pref router, not repeter)
thanks for ur answer