System crash and no flush iax frames

I’ve notice a worring trouble with Asterisk using an IAX trunk.
Sometimes, after a long conversation, between 12hours to 2days, the counters shown by the command : iax2 show stats, starts increasing drastically.

The egress counter shows an accumulation of frames not transmitted.

And as I type the command ps -aux in the linux console, I notice that the process of Asterisk increase is consuption of memory.

Does anyone have an idea about what is happening?