One of the main advantages with 64-bit is getting rid of the memory constraint. As a 32-bit program, CC3+ can only address up to 4GB of memory, but with 64-bit it would be able to use all the memory in you machine, no matter how beefy, for a long time to come.

There are other advantages as well, but for CC3+ that is the biggest advantage.

There's no direct way to find them, I do it by a bit of structured trial and error. I start by figuring out which sheet contains the problematic entities by hiding half of them, figuring out if the problem still persist, if not, it is on one of the hidden sheets, if it continues, it is on the still visible ones. Continuing that way until I am down to one sheet (Takes more effort to write that explanation than actual do it in practice)

Since there where quite a lot of entities on that sheet, I narrowed it further by hiding layers. Could have used the same approach, but I found it faster to do a list of all the entities on the sheet to figure out which layers were involved, and then tested those 1 by one.

This lead me to the SYMBOLS sheet and FURNITURE layer if my mind serves me correctly.

Still a bunch of visible entities, so I just proceeded erasing a good bunch of them at a time, retrying between each batch. Turns out that the problem still persisted after deleting all visible entities. And that makes it easy to find the culprits, since the last step is now just doing a info -> list, then hit a (or right click o get the selection menu and select all) and do it. And voila, the list command shows me the culprits.

I have no idea why these corrupted entities show up in the first place. I've never had that happen to me personally, but maps with corrupted entities like that do show up in the forums every now and then. And this also brings up the point why it is so difficult to fix those bugs, they're nearly impossible to reproduce. A corrupted map posted by a user don't show how it happened, and the developers struggle to reproduce it so they can find and fix the issues. I don't find anything familiar with the way you describe CC3+ yourself. Granted, I have experienced crashes every now and then, but it's not something that happens often. And my maps have never corrupted.

Necro is applied when someone posts after a thread have been dead for more than a year. It serves to tell others that this is a very old thread and just to keep an extra eye out for irregularities, such as spammers, as many love to post on old cases. The necro flag should go away after five or so new posts, indicating that the discussion is active again.

There are three entities in your map that is causing problems. Not sure how they occurred, but if you erase them, the zooming problem should go away.

These are entity numbers 114189, 114190, 115004

To erase an entity by it,s number, click :CC2ERASE: then right click inside the drawing area and from the selection pop-up, select more -> Entity Tag #. The command prompt should then show a Tag #: prompt. Type in one of the entity numbers from my list above and hit enter. If you did this correctly, the command prompt should show that you have one entity selected. Now, right click again and select Do It. Repeat for the remaining two entity numbers.

No, CC3+ doesn't have a way to create a gradient, you'll need to use an external raster file as a fill or a symbol.

The default symbol sheet isn't a global default, but rather a per-symbol setting, allowing CC3+ to be set up with different symbols on different sheets. The default sheet for a symbol is stored individually for each symbol in the symbol catalog. To change this you need to edit the symbol catalog by loading it in to the main editor (as a map) instead of in the symbol catalog window. You can now open the symbol manager, and from there access, the properties of the symbols to change their sheet.

Note that I do not recommend you edit this, rather, take advantage of the naming scheme for sheets. Most symbols are set up to go to the SYMBOLS* sheet. Notice the asterisk. That basically means that if the currently active sheet starts with the text SYMBOLS they will be placed there, but if it doesn't, they go to SYMBOLS. You can take advantage of this and name your sheets things like SYMBOLS SECRET, SYMBOLS HIDDEN and whatever.

The layer setting is controlled by the symbol catalog setting, and is set when you load in the symbol catalog. You can see this setting for each of your catalogs by clicking :CC2SYMICOND: then clicking Advanced. Now pick any symbol catalog setting in the list and then click properties to control what layer that catalog uses.