There are ten other things that I'm constantly cursing about. Like, I just tried to do a simple garbage matte, and the program froze up; and I spent about an hour on it and couldn't figure it out in the end. I'm opening up an old Macbook with FCP 7 on it to do simple tasks that Adobe can't seem to handle or has made beyond confusing. Just like when their moderators reply on these threads and try to explain things. Word salad. Adobe has made a terrible program. Aside from its rendering capabilities, the rest of it is trash.
I’m sorry about the problem you’re experiencing. If you could give us more details about the issue along with your system information, we could try to fix it. Perhaps you could share your workflow for creating the matte too so we could see where things are going wrong. We’re here to help.