ItemNotFoundException from ChannelManager with Content Blocks Plugin

Versions: Reproduced in both
a) Hippo 7.9.8 (Channel-Manager 2.26.09) with Content Blocks Plugin 1.11.04 [1]
b) Hippo 7.9.6 (Channel-Manager 2.26.07) with Content Blocks Plugin 1.11.04 [1]

Use case:
1) Create a document in CMS
2) Append a file to it as "hippo:resource", using Content Blocks Plugin
3) Save & close document
4) Go to Channel-Manager and find the document
5) Click the edit-button, make a small change and click save

The result is an javax.jcr.ItemNotFoundException with an id which doesn't exist, a broken jcr session (logout & -in necessary) and the document is in a broken state.

This only appears if we first append a file as hippo:resource to the document and than edit it using the Channel-Manager. Editing it direct by CMS works fine. The file can be quite small.

I couldn't find anything in this regard on the forum, website, Jira or web.
Does anyone had the same problem, an idea or solution?

See corresponding question on forum [2]

[1] http://content-blocks.forge.onehippo.org/
[2] https://groups.google.com/forum/#!topic/hippo-community/VKxo6FzZbH4