Most of the time, RPi2 send a continuous beep sound from the I2S DAC output and is not anymore under control from putty, so, Yes it is RPi2 that crashes.

Once upon a time, i have xruns errors although jackd is in softmode and this whatever the buffer size.

I didn't experience problems when the RPi2 was running only Jackd/jconvolver/Squeezelite (non RT).

I had the problem when running also squeezebox server (RT).

I had similar problems (buffer issues) with RPi2 was running BruteFIR/Squeezelite/Squeezebox server, both RT and non RT.

I may have forgotten to try Jackd/jconvolver/Squeezelite + Squeezebox server (non RT).

I will make this and report back.

Thank you,

Jean