... in all course lessons, products and blog posts.
I thought, if I used Gutenberg early on, I would have less work editing my content. Now I have more work.

Nicole
May I ask for a bit more information?
Did this problem happen for you only after upgrading from Gutenberg 3.5 to 3.6 or were you referring to updating from WordPress 4.9.7 to 4.9.8?
May I ask you to include the version numbers for the WooCommerce and course plugins you are currently using?
After upgrading from Gutenberg 3.0.1 (the last version without the issue of random redirects when clicking edit) to the latest version.
Also, I have the latest versions of Wordpress, WooCommerce and LearnDash running.
Hope this helps.
Noting for reference that the latest versions are: WordPress 4.9.8, WooCommerce 3.4.4, LearnDash 2.5.8.2 # and adding the Needs Testing label.
I've had similar issues on one of my test sites, after upgrading to 3.6. I've now got multiple pages that show the "This block has been modified externally" error on a variety of different blocks. e.g. Heading blocks, List blocks, Text Column Blocks, Image Blocks.

I've experienced the same as @maddisondesigns describes.
@maddisondesigns @kallehauge could you confirm for me if you were using the exact same plugins @nmschaller mentioned (WooCommerce 3.4.4, LearnDash 2.5.8.2)?
@designsimply I've never used LearnDash, so I've never had it installed. That test site from my screenshot above does have WooCommerce activated though.
Right now, I am using
WP Version: 4.9.8
WC Database Version: 3.4.6
VaultPress: by Automattic β 1.9.6
Akismet Anti-Spam: by Automattic β 4.0.8
bbPress: by The bbPress Community β 2.5.14
BuddyPress: by The BuddyPress Community β 3.2.0
Functionality: by Shea Bunge β 2.0.0
Nicole Schaller: by β 2016.07.13
Gutenberg - Support for WooCommerce: by conschneider β 0.1 β Not tested with the active version of WooCommerce
Gutenberg: by Gutenberg Team β 3.9.0
Jetpack by WordPress.com: by Automattic β 6.6.1
LearnDash Course Grid: by LearnDash β 1.5.1
LearnDash ProPanel: by LearnDash β 2.1.3
LearnDash WooCommerce Integration: by LearnDash β 1.4.0 β Not tested with the active version of WooCommerce
MiwoFTP: by Miwisoft LLC β 1.0.6
Official MailerLite Sign Up Forms: by MailerGroup β 1.2.7
Reading Time WP: by Jason Yingling β 1.2.2
SendGrid: by SendGrid β 1.11.8
LearnDash LMS: by LearnDash β 2.5.9
WooCommerce Gutenberg Products Block: by Automattic β 1.1.2
WooCommerce EU VAT Number: by WooCommerce β 2.3.11
WooCommerce Stripe Gateway: by WooCommerce β 4.1.10
WooCommerce: by Automattic β 3.4.6
WP-Piwik: by AndrΓ© BrΓ€kling β 1.0.19
Name: Twenty Seventeen
Version: 1.7
Author URL: https://wordpress.org/
Child Theme: β β If you are modifying WooCommerce on a parent theme that you did not build personally we recommend using a child theme. See: How to create a child theme
WooCommerce Support: β
Hope this helps.
Heading block is working fine with the latest release closing this. We can reopen if you are still facing the issue.