high load cpu with hotspot?

hi
my rb433 has ros 5.2. my problem is that when hotspot users be 7-10 the cpu load will be 100%

all off active servies in my RB is :
pppoe server
hotspot
pptp client
dns cache

max online user in hotspot+pppoe= 25 user and total BW=2mbps

only disabling the hotspot can return cpu load to normal obout 10%

It’s the time to update.