Loop Protection on 1920 jg925a

Hi

I've some 1920-24g-Poe+ (jg925a) with fiber uplink.

I want to enable the loop guard to prevent the network from loop.

I've the MSTP configured by default (enable), in network->mstp->port setup I've selected all port and enable loop protection.

If I create a loop network works without problems but where I can find the log of loop?

In the syslog I seen the attached file 

Can You help me to discover the correct log?

my best regards