Crash on iOS with MergExt scroller: how to detect the cause

[trevix]

My stack, while working fine on Mac (OS X10.10.5), crash after opening, both on the iOS simulator and on the fiscal device (iPad2).
This happens after the "openCard" msg and has something to do with the MergExt Merg Data Grid Scroller of the first card.
If there is no data on it, the stack opens regularly...

The crash report is an impossible read, to me:

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x000000000000001c

Any idea on how to find the problem ?