Monthly Full Backup with Weekly Incremental Backup advice

Hi, I have a client with Acronis Backup 11.7

It's setup with a Monthly Full Backup Job that the client uses to backup their server. Then the client extracts the archive file and puts it on another drive for safekeeping, and then the client deletes the archive from the destination hard drive.
There's also a Weekly Incremental Backup Job that's supposed to be done, but for some reason isn't working properly. 

Because it wasn't working, I reconfigured the weekly incremental backup job two weeks ago so its done every friday. I lauched it manually and it worked and then I let it do its thing on its own friday as its supposed to do. Monday morning I checked it again, and the backup worked without errors or warnings.

Last friday I got an error. The error was saying that there's already an archive with the same name (Archive(1)) in the destination folder. 

I checked and it did have the archive(1).TIB file that was created automatically with the monthly backup job that the client forgot to delete. The file dates back to the 3rd of October.

So I deleted the destination drive's content and reconfigured the weekly backup job with a different file name than the one from the monthly backup job.

Now I'm wondering though, how is this thing supposed to be configured to work properly?
Are my two jobs' files supposed to be named the same? 
If they're not supposed to be the same, how come it worked the first week?

If they aren't, the software tells me there isn't enough space in the destination drive.

If they are, the software tells me there's already an archive with the same name in the destination drive...

I tried to look into the documentation before posting here, but I couldn't find anything explicitly pertinent to what I'm trying to do. 
 

Is it simply that the client needs to upgrade the size of the destination hard drive so it can fit both the weekly and monthly backup jobs? 

Looking for any advice.