I located the folder and deleted it. When I opened the dSS Console and clicked on the problematic clientID it gave me the blue baloon that it cached the settings locally. After that I tried to assign a template to it and upload rules and config and it gave me the same error as stated in the OP. So, no luck with that I suppose, unless I did something wrong
I compared the dsupportsuite.ini file with another client's .ini file and I noticed some differences. It seems that I cannot "write" on this folder so that the correct ini file and other files populate the folder. But this happens only on this one folder and this one clientID. I double checked if there is a problem with the clientID naming but it is as it should, no special characters, no spaces, it's not even the biggest name on my list.