Styles cause lag on Block insertion and selection

[getdave]

Describe the bug
Inserting the Navigation block causes a perceivable lag in the editor interface before the block appears and is useable. This also happens when re-selecting the block having focused elsewhere.

The culprit appears to be the Block styles. This is likely due to the perf costs of rendering the BlockPreview component.

To reproduce
Steps to reproduce the behavior:

0. On master branch.
1. Create Post
2. Insert Nav Block
3. See lag before you are able to interact with the block/editor again.
4. Click away from Nav Block so it is no longer "focused".
5. Click on Nav Block again to re-select it. Again, notice the lag before it becomes interactive.

Expected behavior
There should be no perceivable lag.

Screenshots
Here are some videos to illustrate the issue.

• Lag visible with Block styles in place - https://d.pr/v/RSpTnJ.
• No lag visible with Block styles removed - https://d.pr/v/kEV86x

Editor version (please complete the following information):

• WordPress version: [e.g: 5.5]: it's 5.5
• Plugin
• If the Gutenberg plugin is installed, which version is it? It's the version from master.

Desktop (please complete the following information):

• OS: [e.g. iOS]: MacOS
• Browser Chrome
• Version [e.g. 22] 83

cc @draganescu

[draganescu]

It is interesting to note if this is visible to other blocks as well.

[adamziel]

Unfortunately I am unable to reproduce the visible lag. Still, the BlockPreview component is pretty slow indeed. Recently I added a memo() which helped avoid costly re-rendering (#21973) - I wonder if it's failing somehow and the component is getting rendered multiple times?

[draganescu]

I will edit this issue to be more generic as Block styles, if the problem is observed consistently, are in all the blocks that support them, not just in navigation.

[getdave]

I'm going to close this as I can't reproduce in incognito mode so I think it must be one of my extensions.