Probably it's another issue, but it looks the same. So the problem is that with ingo you can edit sieve scripts on IMAP server, but changes can't be saved to LDAP server. Below is the relevant (IMHO) error from LDAP log file:
Mar 1 18:16:20 [slapd] conn=94 op=1 BIND dn="cn=Test Test,ou=Users,dc=net,dc=home" method=128_
Mar 1 18:16:20 [slapd] conn=94 op=1 RESULT tag=97 err=53 text=unauthenticated bind (DN with no password) disallowed_
Mar 1 18:16:20 [slapd] conn=94 op=2 SRCH base="dc=net,dc=home" scope=2 deref=0 filter="(mail=test@net.home)"_
Mar 1 18:16:20 [slapd] conn=94 op=2 SRCH attr=hordePrefs_
.....
Mar 1 18:16:20 [slapd] conn=94 op=4 SRCH base="dc=net,dc=home" scope=2 deref=0 filter="(mail=test@net.home)"_
Mar 1 18:16:20 [slapd] conn=94 op=4 SRCH attr=objectclass_
Mar 1 18:16:20 [slapd] conn=94 op=4 SEARCH RESULT tag=101 err=0 nentries=1 text=_
Mar 1 18:16:20 [slapd] conn=94 op=5 SRCH base="dc=net,dc=home" scope=2 deref=0 filter="(uid=test@net.home)"_
Mar 1 18:16:20 [slapd] conn=94 op=5 SRCH attr=objectclass_
Mar 1 18:16:20 [slapd] conn=94 op=5 SEARCH RESULT tag=101 err=0 nentries=0 text=_
Mar 1 18:16:20 [slapd] conn=94 op=6 MOD dn="cn=Test Test,ou=Users,dc=net,dc=home"_
Mar 1 18:16:20 [slapd] conn=94 op=6 MOD attr=ingoPrefs_
Mar 1 18:16:20 [slapd] conn=94 op=6 RESULT tag=103 err=8 text=modifications require authentication_
Mar 1 18:16:20 [slapd] conn=94 op=7 UNBIND_
Mar 1 18:16:20 [slapd] conn=94 fd=24 closed_
Switching to the older version (1.13) solves the problem.