Quality of SPA921/SPA941 g729

Any person has compared the quality g729 on the telephones of the BATH with other telephones?

I have had a number of complaints lately that calls terrible healthy with g729 - the users obtain the distortion etc. It is not definitively an edition of the width of band, we works the BATH in separated connections to the access of the Internet.

We blinded customes proven with some SPA921, 941 ' then s and some telephones of Grandstream (ick, I know), and in each single case, disclosed the BATH sounded like crap, but the sounded Grandstream really clear. This is through several ITSP, so anyone cannot really be a ITSP problem.

I thought that it can have been right some telephones, but it looks like to have happened his yet I has proven until the moment. g711 sounds absolutely fine, but g729 is marginal, perhaps 60% of the time that sounds the authorization but the rest of the time is as if the processor on the telephone is overloading ?

The BATH is working 5.1.5. I am not safe if she is any this hornada of telephones, a failure of the design of the hardware, or of a thing of the softwares unalterable.

Could some other with some diverse telephones try with 729 and compare them?