I am using ODK Collect 1.27.1, because I need the added features discussed in other threads today. I assume that KoboCollect 1.27.1 which will be out soon has similar problems. If someone has access to KoboCollect 1.27, please check:
This is essentially the usual suspect test project posted several time, but with manual entry instead of barcodes. 687 is a valid barcode. Enter it, works fine.
Now press backspace for 68. Or add another digit, e.g. 6871. Both crash the app on my Android tablet.