I believe now that it's the wideband filter. Designed to go bad or so it seems... and not just on Kenwood ham gear but also on LMR too.
The link below explains it in better detail.
Since RR is highly indexed into google and yahoo groups is not, I'm sure others will be ending up here when they search the web for this problem with their tm-271a.
It does require membership to view the post unfortunately.