Wow, I didn't even realize guides could be locked!
Yep, after quick test, I can reproduce that.....well, the part where they're unlocked when you re-open the file. I'd have to make locking guides part of my workflow, to be able to test what makes them unlocked otherwise.
Interesting. I see that you can still select a locked guide (by double-clicking). Like if you needed to change its position. Or I guess that's how you would unlock them.
For the part where they come unlocked during drawing, that would probably be a bug. Although it would be better if you could figure out how to reproduce it, before you report it. I'm not sure whether it would be a feature request or a bug, but I'm guessing that keeping them locked after closing and re-opening is something you'd have to ask for. Did you search in Launchpad yet?
Oh, look at this! Already reported. And it's good sign that someone is committed to work on it.
https://bugs.launchpad.net/inkscape/+bug/1643179I know there's an extension for creating guides, which as I recall was added to Inkscape just before the built-in guides got a bit of an upgrade. But I don't see a lock feature in that extension. There might be a 2nd extension though. Let's see if I can find out....
Oh wow, there are 2 extensions for creating guides, besides the one that comes installed (Extensions menu > Render > Guides Creator). Although again, I don't see any locking feature there.
Here's one:
https://github.com/sambody/inkscape-guide-toolsHhm, ok I think this 2nd one might be the one which is now installed, because it has the same name. But who knows, maybe not. In case you want to investigate:
https://github.com/Ale-/inkscape-gs(And there's another extension which will delete all guides in one step. But I doubt if it has locking.)
I think I might have made a feature request for guides to be assigned to layers. And if that came to be, the guides theoretically could be locked with the layer. But I'd have to search to be sure I actually made the request. I think I just asked about it on a mailing list, but decided not to make the report on LP.