No known issues, no. What I'm wondering is whether the crash is really random: That would, for example, suggest that the iPad Air is running out of memory at some point, which is theoretically possible (1st generation Airs weren't super-strong hardware spec-wise, and iOS 11 tends to be a bit more resource-intensive than iOS 9; or the iPad in question might have some bad RAM). Alternatively, the crash might just appear to be random, but actually there is something systematic going on: A specific audio or image file used in a specific trial might cause a problem, but because the specific trial is run at different times in the various conditions in your script, this ends up looking random.
If you run only the 1st condition in the script a couple of times, i.e.
/ groupassignment = groupnumber
/ subjects = (1 of 8)
/ blocks = [1=test1]
executing <block test1>, when -- approximately -- does the crash occur during each respective run?