Check out edelivery.oracle.com. There you should be able to find all earlier versions.
Make sure you apply also all the relevant patchsets, at least the same you have installed on the server. I'd recommend to apply all the available patchsets for 12.1.3.
This was a quite buggy release with a lot of improvements and bugfixes a long the way.
Also, since you're still on 12.1.3, which is only a little less ancient than 11g, I'd highly recommend talking with your colleagues and admins to define an upgrade path. You would surely do yourselves (both the devs as wel as the admins) a favor upgrading to 188.8.131.52.
thanks for the answer. Sadly I can't find this version in edelivery.oracle.com. There is for example versione 11.1.7 but not 12.1.3, it's strange. Do you know same other link where I can find it? I know that upgrade wold be the best solution, in fact, I already recommended this and I'll try to work on but I don't think it will be soon and in the meanwhile potentially I have to do fixes on deployed workflows..
In edelivery search for download package, on the term "BPM":
I guess you can also search on SOA Suite.
Then scroll down to "Select DLP: Oracle SOA Suite for Oracle Middleware 184.108.40.206.0 ( BPM )" and select it. I agree, it might be confusing.
Then check it out under "View Items" and follow the instructions to:
Uncheck all except the "Oracle Business Process Management 220.127.116.11.0" option and continue.
It rbrings you here:
Click on the link before "Oracle Business Process Management 18.104.22.168.0 - Quick Start for Developers":
And there it is!