Element x doesn’t exist in the site y when saving new Matrix block

[sjelfull]

Description

After upgrading to 3.0.30, i'm getting this error when saving a new entry (with a new Matrix block):

Element 9350 doesn’t exist in the site 2.

This is triggered in services/Matrix.php:674.

Steps to reproduce

1. Create a Matrix field with “Manage blocks on a per-site basis” enabled.
2. Add the field to a section enabled for multiple sites, with “Propagate entries across all enabled sites?” enabled.
3. Try to save a new entry in that section, with at least one block.

Additional info

• Craft version: 3.0.30

[mildlygeeky]

I am having the same issue, though I am running 3.0.29

[brandonkelly]

Just released 3.0.30.1 with a fix for this.

@mildlygeeky yeah it was introduced in 3.0.29.

[mildlygeeky]

Thanks @brandonkelly!