I have inherited a Panasonic KX-TG2570B 2.4GHz Cordless Phone. At times,
the handset seems to be over-modulated, and at other times there is a high
level of static. Interestingly, the battery never seems to get over 33%
charge (3 block bar graph display). Cleaned all contacts (internal and
external) and have even tried a new battery and got the same results.
During charging, the battery compartment gets warm, but I am not sure if
this is normal or another symptom. The speakerphone in the handset works
perfectly.

Any ideas on what might be wrong or what to try next?

Thanks!