I see the same garbage character for multiple search filters in the trace log.
But it differs a bit..
FYI: I'm reading this as UTF-8.. but I have not ran the arslsync with UTF-8 yet, cant install the locale today.
Search 1
(&(objectClass=user)(memberOf:1.2.840.113556.1.4.1941:=CN=...,OU=...,DC))
Search 2
(&(objectClass=user)(memberOf:1.2.840.113556.1.4.1941:=CN=...,OU=...,
Search 3
(&(objectClass=user)(memberOf:1.2.840.113556.1.4.1941:=CN=...,OU=...,DC=test
Ye well as you say, it could look like log bug