I pushed a template from the editor to my E1, and all the toggle buttons lost their text.
I created an empty template containing a single button, and the same thing occurred.
No lua or anything special. Just text-less buttons.
The json seems to still have the Name present, it just isn’t getting rendered for some reason.
weird. I rebooted the E1, and now the text appears on the buttons.
probably the font has scrambled up when reading from the card, perhaps because at that moment the E1 was not getting enough power? I recall having had the same issue a long time ago, but my memory doesn’t serve me well 
I would expect that would have affected all text though, and it was just the toggle buttons. The text under faders for eg was fine.
Hopefully a one-off, but will report again if it reoccurs.