I'm getting an error about this mod when trying to use Upgrade Planner on a blueprint:

The mod Belt Buffer caused a non-recoverable error.
Please report this error to the mod author.

Error while running event belt_buffer::on_player_configured_blueprint (ID 70)
Item is not blueprint.
stack traceback:
belt_buffer/control.lua:273: in function <belt_buffer/control.lua:267>
stack traceback:
[C]: in function 'get_blueprint_entities'
belt_buffer/control.lua:273: in function <belt_buffer/control.lua:267>

I don't know why I would have this coming up. The blueprint I'm upgrading doesn't contain any belt buffers. It's a blueprint I use for FARL that contains railway entities. This started coming up in version 0.17.69. I have not seen it before.

Now I'll see what can be done, then unsubscribe, thanks for the error report

And what version of the mod do you have installed?
This error occurred in version 0.17.4 and was fixed in version 0.17.5

In any case, try installing
Version: 0.17.6
Date: 25.09.2019.
Bags:
- When the pipeline buffer was destroyed, the robots did not restore it, referring to the absence of an item in the warehouse, although it was there.

P / s
Not in version: 0.17.5 not in version: 0.17.6 I was not able to cause this error.