This is usually the result of the probe timers being configured incorrectly.
for instance if interval is less than recieve timeout , or passdetect interval is less than interval or receive timeout or open timeout.
A clue that this may the the case id to do a show probe detail and look at skipped probes if you see skipped probes you need to adkust timing.
you can use
show resource internal socket
to monitor socket usage.
what are your probe settings ?
You probably want to also get to a later code version such as A3(2.5) or (2.6) The number of sockets available were increased in the later code.
Regards