I've been wondering what could be in the chassis that damaged the PU seeing that this is the chassis they've been using since testing, until I saw this:
http://en.hondaracingf1.com/insights/Ba ... day-1.html
Look at the rear end of the STR13 and compare it with this:
https://cdn-6.motorsport.com/images/mgl ... ser-de.jpg
Looks like they finally got the tight rear package
Something also tells me that was one of the culprits of the issue they had.
Furthermore, and just speculation on my part at this point, is that together with the tighter rear end, they might have also tightened a bit the PU packaging together with the new PU, bringing a complete update to the test. That could well explain why the PU might have been damaged by the chassis and of course, that's why you need testing.
That would also mean that updates will not probably come before Canada, so that they have enough time to fix any issues they find during testing.