SQL Server : change SSIS package configuration (connection string)

I'm maintaining a project using Microsoft SQL Server 2016 (SP1) (according to this script) which heavily depends on recurring jobs (mirroring certain external db's and so on).

Especially the mirroring jobs are essentially based on SSIS packages which define a datasource, then execute a hardcoded SQL query and afterwards store the results in the specified destination.

Unfortunately the source databases where moved to a different domain and thus aren't accessible via the previous url.

My issue right now is that I simply have to change the source destination url but I'm not able to do that. There are plenty of ways to 'modify' SSIS packages but none of them seem to work with me.

What I managed (and seems the most promising) to do is to open the 'Integration Services...' part of my db, export the jobs to my desktop, modify them with Notepad and reimport them. And they seem to work if I execute them separately. But as soon as I try to execute the packages via SQL Server Agent it fails screaming:

Description: Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B "Key not valid for use in specified state."

Does somebody know whats going on here and how I'm able to solve this? No password or username changed, only the connection string.

Is it even possible to manage a package like that?

Thank you for your help!

After further investigation I detected that even a newly created job didn't run properly. It was kind of strange that a package would run without any issues while directly executed but not via the SQL Server Agent, so I assumed it may be a rights issue and it was!

Somehow the Server Agent wasn't allowed to decrypt (although I never changed the executing user of a step) the password anymore.

I was able to work around my issue by simply creating each SSIS package again (some click hell but ok) but this time I secured 'sensitive data' with a password instead of the users key.

Afterwards I had to change each job step with a reference to to the damaged ssis packages and obviously type in the new passwords.

Seems to work again.

Thanks anyway