topic: subtopic that adds prefix to all block machine names


On my site, I have created a subtopic of a subtopic using this as a guide to configure this https://www.drupal.org/docs/8/theming-drupal-8/creating-a-drupal -8-sub-theme -or-sub-theme-of-sub-theme and works with handover of all css / js / regions but for some reason it is renaming all blocks with the subtopic prefix.

So for example I have a block with a primary navigation machine name when I install / set the subtopic by default it will change this block to theme3_mainnavigation.

I have tried to delete the block and put it back with the same main navigation name, but I run into a problem where a message will appear saying that this machine name already exists.

Does anyone know how to fix this so that the subtopic uses the machine names of the existing names instead of creating a prefix?

Thanks for any help!