Not aware of any setting that would intentionally or accidently cause this... I'm thinking it may either be a network (repeater or EDACS) 'problem' if its noticable on more than one radio.
Need more information on this though:
Does this happen on your LPE alone, or others LPEs too, or a mix of radios on your system (ie LPE, MRK, Orion, MDX, P7100 etc)?
EDACS or conventional, or a mix of both? If a mix, does it happen on one or the other, or both?
800 or 900 MHz?
Does this happen everywhere you go, or just one particular location?