2.6.1 AP GPS web very slowly, also CLI, ~70 SM connected

I have an AP GPS with 2.6.1 which is very slowly on the web and cli (takes ages to login and to ask for anything).

The AP has ~ 70 CPE connected and is moving ~30-35 Mbps and ~4000 pps. CPEs between 3-5 Km, very good signals (-50 to -65)

I have seen on the CLI these CPU load metrics

Mem: 65268K used, 61700K free, 0K shrd, 0K buff, 25448K cached
CPU:   4% usr   3% sys   0% nic   0% idle   0% io   0% irq  92% sirq
Load average: 3.01 2.18 1.01 6/51 21129

Further on this... I had to change the SSID in order to kick all the CPEs and let the GUI responsible again to upgrade to

Can you please provide any advice on this? Is this a AP limit? Anything I can tune. I'm using WPA2 EAP and radius autentication.

Best regards