When I am adding interfaces and signals to a component in the component editor, I can save the component and then reopen it and many of the interfaces I defined are gone. This also happens when there is an error in one interface. Is there some order I need to follow to correct errors without having to redefine existing interfaces?
Are you finishing the Component Editor and getting the message that it will create a _hw.tcl file? That's where the interfaces and signaling would be saved. There's no limit on signals/interfaces that I know of.
Yes, I finish the component editor and chose to save. At that point, it writes to the _hw.tcl file. The first time I saved my component, I did not include all the interfaces. To add additional interfaces, I edited the component and continued adding. The next time I saved, multiple, previously added components were removed from the .hw.tcl file. I've tried tackling this in different ways, like adding them one at a time and saving in between (very time consuming); however, I always get to a point where the save action removes interfaces that were previously added. At this point, I have opted to edit the tcl file directly and stop using the Component Editor, especially after finding multiple postings in the Community regarding the flakiness of that tool.
When you say you "edited the component and continued adding", do you mean that you right-clicked the custom component in the IP Catalog and selected Edit? That's the way to continue updating an existing custom component using the graphical tool. From your description, it sounds like when you are "editing" a component, you are actually starting over and creating a new _hw.tcl file that is overwriting the old one.
Recent versions of Platform Designer create backup _hw.tcl files (I think they are named _hw.tcl~). Have you checked these backups and compared them to the current _hw.tcl?