eSpace IAD 132e(T) periodically problems

Good day.

1st of all - sorry for my bad english, and (if I missed forum) - please direct me to the rigth one.

My company bougth ~13 Huawei IAD 132e (T).
Now we periodically register some unusial sutiations...

On high-loaded IAD it happens every day or two. (25-32 ports active, 20 simultaneous calls max)
On low-loaded IAD it happens every week or two. (5-15 ports active, 5 simultaneous calls max)
Symptoms:
1*) When calling subscriber: Asterisk reports - Got SIP response 500 "Server Internal Error" back from <IAD_IP>:5060
2*) When subscriber tries to call: Recieve busy tones
2.1) (no logs on asterisk at max. verbose)
3*) Subscriber tried to transfer call with Flash - busy tones recieved
3.1) algorythm (attended transfer): [1]answer call, [2]press flash, [3]call another subsc., [4]answered by subsc., [5]hang up call
3.2) symptom: after [3] client returns to subscriber.
4) Busy2 indicator - continuous light
*Symptoms 1,2,3 are shown absolutely in a random way on any port.

After IAD reboot - situation becomes normal and symptoms disappears.

display version
  Equipment type   : eSpace IAD132E(T)
  eSpace IAD132E(T) mainboard version information
    PCB      version : AG11CVP.2 REV.A
    Product  name    : TS3202
    Program  version : V300R001C07SPC600
    BIOS     version : 1036
    DSP      version : VoIP V100R003C01
    CPLD-A   version : 101
    CPLD-B   version : 106
    Slic     version : 000
  SLOT 1 ASID interface board version information
    PCB      version : AG11ASI.1
    Chip     version : 0
    CPLD     version : N/A
  SLOT 2 ASID interface board version information
    PCB      version : AG11ASI.1
    Chip     version : 0
    CPLD     version : N/A

So... questions:
1) What means continuous light on "Busy2" indicator?
2) Reboot takes 3-4 min... it is too much for standart business day :( What else can be done to solve or avoid such situations?