[FSE] "Save" flow activates inconsistently

[annezazu]

Description

This is feedback from the fourth call for testing for the FSE Outreach Program:

Another thing I noticed was that some small changes, like adjusting the percentage width of the individual columns didn’t activate the “update design” button. It stayed inactive until I did some other change like a text change.

Essentially, the Update Design button seems to appear inconsistently. This is something I've noticed in the past but wasn't quite sure how best to replicate until now. The pattern seems to be changes related to alignment/spacing/width and it seems to only happen after one first saves changes related to the initial alignment/spacing/width.

Step-by-step reproduction instructions

1. Set up a test site with the latest version of Gutenberg and the TT1 blocks theme.
2. Head to the Site Editor (beta) tab.
3. Change the width of one of the columns in the header template.
4. Select "update design"
5. Make an additional change to the same column width.
6. Notice the "update design" option doesn't appear as clickable making it impossible to save changes without further action.

Expected behaviour

Expect the "Update Design" option to be available.

Actual behaviour

Unable to save changes due to "Update Design" not kicking in.

Screenshots or screen recording (optional)

Here's an example with adjusting column width:

update.design.mov

Here's an example while adjusting the positioning of the navigation block:

nav.block.update.design.mov

WordPress information

• WordPress version: 5.7
• Gutenberg version: 10.3.1
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? TT1 Blocks

Device information

• Device: Desktop
• Operating system: MacOS
• Browser: Chrome 88

[annezazu]

Another example from the sixth call for testing while trying to replicate something:

Screen.Recording.2021-05-14.at.6.32.17.PM.mov

[annezazu]

Another example of this happening: adjusting the width of the Post Title Block doesn't trigger the option to save. One has to update the Post Title in order for it to offer the option. This was found by @synora!

[annezazu]

Another example of this behavior: #36409

[annezazu]

I haven't seen reports of this nor have I experienced it in a long time! Going to close this out as likely irrelevant now. Can reopen if needed.