There is no need to mix many instruments. Task can be done by sed only
sed '/^INFO\|^DEBUG\|^TRACE|^ERROR^INFO\|^DEBUG\|^TRACE\|^ERROR/{
/Logger2/{
:1
N
/\nINFO\|\nDEBUG\|\nTRACE|\nERROR\nINFO\|\nDEBUG\|\nTRACE\|\nERROR/!s/\n//
$!t1
D }
}' log.entry