R750 with ZD1200 slow throughput on Laptop with good RSSI and SNR

[anirut_thachuen]

We recently switched to four R750 AP's in our office, where we have existing R600 AP's (3 now in use) in an office with 450+ clients.

The R750 clients (laptops) are experiencing slow throughput 1-4 Mbps download; signal RSSI and SNR are good and stable.  No reports of slow throughput with clients connected to R600 AP.

One example the laptop is within line of sight of the AP (R750 with 100+ clients) about 10 meters away

• signal RSSI and SNR are good to excellent (-65 to -72 RSSI and 28-30 SNR)
• throughput is slow using the speed flex test laptop to ZD 2-5 Mbps
• Speed flex AP to ZD is consistent 900+ Mbps to 1Gbps
• Ping times laptop to AP and DG is triple to quad digit TTL

When the wireless card is toggled off and on the throughput is back to normal 400Mbps + on speed flex

(wireless card has been updated to latest driver and roaming aggressiveness is set to Medium- High)

The throughput will become slow again over time.

I've also notice the clients sitting immediately under the same R750 AP do not experience slow throughput.

Could this be the same issue as support.ruckuswireless.com/articles/000009854 the AP must have PoH/uPoE to function properly?

Is there a configuration that is throttling the throughput of some clients and not others based on the proximity or signal strength of their connection?

Are there additional trouble shooting steps that can be done to find the root cause?

ZD firmware ver 10.4.0.0 build 98

Self healing disabled

Back ground scan every 150 sec

AP's TX adjusted manually 

Only 5Ghz (80Mhz channel) enabled

R750 using 802.3at POE power injectors