There is a bug in opmn.
This is what i got from Oracle support for 11gR 18.104.22.168 version (on linux x64):
Please do the following to apply the patches:
1) Download and apply the patch 15948641, which upgrades FMW to 22.214.171.124.
2) Download and apply both the patches 13055259 and 13490778 on FMw 126.96.36.199. Otherwise. both patches will fail to apply.
If you are on 188.8.131.52 you must upgrade to 184.108.40.206 and apply patch
13055259 (patch 13490778 is already included in 15948641).
If you are on 220.127.116.11 try to apply patch 1305529.