Exception while updating neighbours

I've a new problem after updating my smp server from 15w40b to 15w46a and my squid farm with a minecart hopper system for squid loots at the bottom (implying redstone powered rail, comparator, repeater...)

The server crashes after a few seconds when i'm in the area. i didn't have the problem in 15w40b, it worked with no errors.

I attached the two last crash reports from my server. Hope it could be fixed.