For a single block, if you need to reset the unique IDs, you can do so in the block's context menu.
Generate New Unique IDs option
Why generate new Unique IDs? GenerateBlocks uses the unique ID attribute of its blocks to do style targeting. If you copy/duplicate a block, sometimes the old unique ID carries over, and modifying one block changes the other. With an updated unique ID, the block can be style-independent of other block styles.
When generating new Unique IDs, the conversion works recursively, so any child blocks will also have their unique IDs reset also.
If you need to change the Unique IDs for a group of blocks, wrapping those in a Container block and generating the new Unique IDs for the Container block is recommended.