Congratulations, its very hard to find one with good en blocks, mine cracked within the first month I'm thinking it might come from sitting them on the end block when leaning them against anything like a wall.
The seller said he thinks it comes form dryness. No, its pretty much a design flaw, the design is very flimsy with no extra support or bracing, and the plastic is too thin and brittle, avoid putting it on its sides and if you feel comfortable with it reinforce the inner stress points with some epoxy or hot glue.
If you dont mind me asking how much did you got it for? mine completely died on me about a month ago after 13 years of hard work (not a single board is salvageable) along with 72 MB of Ram And the MOSS board so im looking for the most beat up worn down cosmetically TEX that i can get that works, so im wondering whats the ballpark