Netmetal5 rebooting when running btest

Hello everyone, i found a problem with a Netmetal5+Ubnt AMO5g13: when running a btest involving the Netmetal5 and an SXTLite5, the Netmetal autoreboot.
The scheme is:

RB2011il-in ---------- Netmetal5+Omni ------------ SXTLite5 (x 5)

If i run the test from RB2011 towards a well-connected SXTLite5 there’s no problem, but if i do the same towards a bad-linked one (es. -69/-74 with 28 StN) the Netmetal reboot itself; the same if i run the test from one SXT towards the RB2011.
Netmetal has 6.37.5 installed, the problem occurs either with nv2 or 802.11. Netmetal and SXTs have ethernet and wlan bridged together (protocol mode=none).

Anyone knows how to stop the reboots?
Thank you in advance.