So in reporting the last bug I found, I discovered this one as well. If I leave the server while in the sandbox and come back, the "Blueprint Sandboxes" tab in the crafting menu is gone when I come back. I can workaround this by just leaving the sandbox and re-entering it. Happens in current version 1.4.2.

I have this listed as a known bug, and if it's what I think it is (based on your other posts), then I think it's the same situation or highly related. I know it happens when you are inside a Sandbox, leave the game, upgrade the mod, then enter the game again inside of that Sandbox. I have probably done something wrong with the Forces somewhere, because I have workarounds now that keep re-enabling these Recipes, and this is a case where I don't have a working workaround. I'll keep investigating, especially if it consistently happens when leaving/joining a Server (without any upgrade in-between).