UEXT modules I2C IRQ UART1 conflict

[granite_crusher]

dear Olimex,
I observed that sometimes board fails to boot or restarts with UEXT (I2C) mods plugged in;
If I wire i2c,3v3 and gnd to UEXT except IRQ when never problems appear, and tests provided in git (for MOD-MAG and MOD-SMB380) works ok. If I boot with UEXT ( with those modules plugged in) and have UART1 connection, U-boot console as linux console is deaf to anything when communicating through UART from PC, until I unplug UEXT modules (or plug with custom cable without IRQ). I think sometimes this makes u-boot to fail. my few questions:
1. What for are IRQ used in those modules?
2. Is it safe to use modules without this IRQ (especially if I want to use MOD-GPS on UART1(UEXT) with MOD-MAG and MOD-SMBC380 on UEXT)? Demos from git work without this IRQ