You can only drop a small kitchen scale so many times before the plastic cover / weighing tray breaks:
The trick was to anchor the cover to the glass plate with the big clamp so that the smaller clamps could exert force straight down on the edge, without flipping the lid due to the bevel. With that all set up: apply IPS #4 to the broken edges, insert pieces, apply clamps, wait overnight.
For the record, my morning mug o’ green tea starts with 4 (-0.0 +0.4) g of leaves…
The Smell of Molten Projects in the Morning 
At first I wondered why you were gluing the cover to the glass plate, before I realized you were using the glass plate as a force spreader. It’s always important to have enough clamps. I watched a video of someone assembling a wood frame, just using painters tape to hold it together while the glue cured, then having to fix the resulting gaps, all the while thinking to myself “Why aren’t you using clamps, lots of clamps?”.
That would be what we call in the trade an “unanticipated outcome”, which, I assure you, never happens around here. [mutter]